Rudolf Carnap Bibliography Creator

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Complete Bibliography

The table below includes all the bibliographic resources defined in this encyclopedia:

Citation KeyCitation Text
Adamson (2015)Adamson, Peter. (2015) Al-Kindi. In Zalta (Ed.) (2016). Retrieved from https://plato.stanford.edu/entries/al-kindi/#GreInf.
Aiton (1958)Aiton, Eric J. (1958) The Vortex Theory of Planetary Motion. Annals of Science 14, 157-172.
Allain (2016)Allain, Rhett. (2016) Using Gravitational Waves to Pinpoint Colliding Black Holes. Wired. Retrieved from http://www.wired.com/2016/02/using-gravitational-waves-to-pinpoint-colliding-black-holes/.
Allen (1988)Allen, Paul. (1988) Ernan McMullin and Critical Realism in the Science-Theology Dialogue. Ashgate Publishing Limited.
Allén (Ed.) (1989)Allén, Sture. (Ed.). (1989) Possible Worlds in Humanities, Arts and Sciences: Proceedings of Nobel Symposium 65. De Gruyter.
Anagnostopoulos (2009)Anagnostopoulos, Georgios. (Ed.). (2009) A Companion To Aristotle. Wiley-Blackwell.
Anagnostopoulos (2009b)Anagnostopoulos, Georgios. (2009) Aristotle's Life. In Anagnostopoulos (2009), 3-13.
Anagnostopoulos and Miller (Eds.) (2013)Anagnostopoulos, Georgios and Miller, Fred D. (Eds.). (2013) Reason and Analysis in Ancient Greek Philosophy: Essays in Honor of David Keyt. Springer.
Andersen and Hepburn (2015)Andersen, Hanne and Hepburn, Brian. (2015) Scientific Method. In Zalta (Ed.) (2016). Retrieved from http://plato.stanford.edu/entries/scientific-method/.
Andersen and Hepburn (2018)Andersen, Hanne and Hepburn, Brian. (2018) Scientific Change. Internet Encyclopedia of Philosophy. Retrieved from http://www.iep.utm.edu/s-change/.
Annas and Barnes (Eds.) (1985)Annas, Julia and Barnes, Jonathan. (Eds.). (1985) The Modes of Scepticism: Ancient Texts and Modern Interpretations. Cambridge University Press.
Anstey (2011)Anstey, Peter. (2011) John Locke and Natural Philosophy. Oxford University Press.
Arabatzis (2006)Arabatzis, Theodore. (2006) Representing Electrons: A Biographical Approach to Theoretical Entities. University Of Chicago Press.
Arabatzis and Schickore (2012)Arabatzis, Theodore and Schickore, Jutta. (2012) Ways of Integrating History and Philosophy of Science. Perspectives on Science 20 (4), 395-408.
Ariew (1986)Ariew, Roger. (1986) Descartes as a Critic of Galileo's Scientific Methodology. Synthese 67 (1), 77-90.
Ariew (1992)Ariew, Roger. (1992) Descartes and scholasticism: The intellectual background to Decartes' thought. In Cottingham (Ed.) (1992), 58-90.
Aristotle (1963)Aristotle. (1964) Categories and De Interpretatione. Oxford: Oxford University Press.
Aristotle (1983)Aristotle. (1983) De Generatione et Corruptione. Oxford: Oxford University Press.
Aristotle (1983a)Aristotle. (1983) Physics Books III and IV. Oxford: Oxford University Press.
Aristotle (1984)Aristotle. (1984) Complete Works of Aristotle, Volume 1: The Revised Oxford Translation. Princeton University Press.
Aristotle (1984b)Aristotle. (1984) Physics Books I and II. Oxford: Oxford University Press.
Aristotle (1988)Aristotle. (1988) Metaphysics Books M and N. Oxford: Oxford University Press.
Aristotle (1992)Aristotle. (1992) De Partibus Animalium I and De Generatione Animalium I. Oxford: Oxford University Press.
Aristotle (1992b)Aristotle. (1992) Eudemian Ethics Books I, II, and VIII, Second Edition. Oxford: Oxford University Press.
Aristotle (1993)Aristotle. (1993) Metaphysics: Books gamma, delta, and epsilon. Oxford: Oxford University Press.
Aristotle (1994a)Aristotle. (1994) Posterior Analytics, Second Edition. Oxford: Oxford University Press.
Aristotle (1994b)Aristotle. (1994) Metaphysics Books Z and H. Oxford: Oxford University Press.
Aristotle (1996a)Aristotle. (1996) Politics: Books III and IV. Oxford: Oxford University Press.
Aristotle (1996b)Aristotle. (1996) Politics: Books I and II. Oxford: Oxford University Press.
Aristotle (1997)Aristotle. (1997) Prior Analytics. Oxford: Oxford University Press.
Aristotle (1998)Aristotle. (1998) Politics Books VII and VIII. Oxford: Oxford University Press.
Aristotle (1999a)Aristotle. (1999) Physics, Book VIII. Oxford: Oxford University Press.
Aristotle (1999b)Aristotle. (1999) De Anima II and III. Oxford: Oxford University Press.
Aristotle (1999c)Aristotle. (1999) Politics, Books V and VI Animals. Oxford: Oxford University Press.
Aristotle (1999d)Aristotle. (1999) Nicomachean Ethics, Books VIII and IX. Oxford: Oxford University Press.
Aristotle (200)Aristotle. (2000) Aristotle: Metaphysics Books B and K 1–2. Oxford: Oxford University Press.
Aristotle (2002)Aristotle. (1992) On the Parts of Animals. Oxford: Oxford University Press.
Aristotle (2006)Aristotle. (2006) Metaphysics Theta. Oxford: Oxford University Press.
Aristotle (2006b)Aristotle. (2006) Nicomachean Ethics, Books II-IV. Oxford: Oxford University Press.
Aristotle (2009)Aristotle. (2009) Topics Books I and VIII. Oxford: Oxford University Press.
Aristotle (2015)Aristotle. (2015) De Anima. Oxford: Oxford University Press.
Asquith and Kyburg (Eds.) (1979)Kyburg, Henry and Asquith, Peter. (Eds.). (1979) Current Research in Philosophy of Science: Proceedings of the P.S.A. Critical Research Problems Conference. Philosophy of Science Association.
Ayala (2003)Ayala, Francisco. (2003) Intelligent Design: The Original Version. Theology and Science 1 (1), 9-32.
Ayer (1952)Ayer, Alfred Jules. (1952) Language, Truth and Logic. Dover Publications.
Babich (2003)Babich, Babette. (2003) From Fleck's Denkstil to Kuhn's Paradigm: Conceptual Schemes and Incommensurability. International Studies in the Philosophy of Science 17 (1), 75-92.
Bacon (1613)Bacon, Francis. (1613) The Essaies of Sir Francis Bacon. His Religious Meditations. Places of Perswasion and Disswasion. I. Iaggard.
Bacon (1853)Bacon, Francis. (1853) The Essays, or, Counsels, Civil and Moral. John W. Parker & Son.
Bacon (1855)Bacon, Francis. (1855) The Novum organon, or a true guide to the interpretation of nature. Oxford University Press.
Bacon (1859)Bacon, Francis. (1859) The Works of Francis Bacon, Lord Chancellor of England. Parry & McMillan.
Bacon (1861)Bacon, Francis. (1861) The Works of Francis Bacon. Taggard and Thompson.
Bacon (1874)Bacon, Francis. (1874) The Letters and the Life of Francis Bacon. Longman, Green, Longman, and Roberts..
Bacon (1878)Bacon, Francis. (1878) Bacon’s Novum Organum. Clarendon Press.
Bacon (1898)Bacon, Francis. (1898) Novum Organum or True Suggestions for the Interpretation of Nature. NA.
Bacon (1901a)Bacon, Francis. (1901) The Works of Francis Bacon. NA.
Bacon (1901b)Bacon, Francis. (1901) Novum Organum. Collier.
Bacon (1920)Bacon, Francis. (1920) The Advancement of Learning. Oxford Clarendon Press.
Bacon (1958)Bacon, Francis. (1958) Essays. Everyman's Library.
Bacon (1962)Bacon, Francis. (1962) Essays. J. M. Dent & Sons.
Bacon (1965)Bacon, Francis. (1965) The Advancement of Learning. Everyman's Library.
Bacon (1968)Bacon, Francis. (1968) The Works of Francis Bacon. Garrett.
Bacon (1996a)Bacon, Francis. (1996) Collected Works of Francis Bacon. Routledge/Thoemmes Press.
Bacon (1996b)Bacon, Francis. (1996) The Oxford Francis Bacon VI: Philosophical Studies 1611-1619. Oxford University Press.
Bacon (1998)Bacon, Francis. (1998) The History of the Reign of King Henry VII and Selected Works. Cambridge University Press.
Bacon (2000a)Bacon, Francis. (2000) A Critical Edition of the Major Works. Oxford University Press.
Bacon (2000b)Bacon, Francis. (2000) The Oxford Francis Bacon IV: Advancement of Learning. Oxford University Press.
Bacon (2000c)Bacon, Francis. (2000) The Oxford Francis Bacon XIII: Last Writings. Oxford University Press.
Bacon (2000d)Bacon, Francis. (2000) The Oxford Francis Bacon XV: The Essayes or Counsels, Civill and Morall. Oxford University Press.
Bacon (2004)Bacon, Francis. (2004) The Oxford Francis Bacon XI: Novum Organum. Oxford University Press.
Bacon (2007)Bacon, Francis. (2007) The Oxford Francis Bacon XII: Historia Naturalis. Oxford University Press.
Bacon (2011)Bacon, Francis. (2011) The Oxford Francis Bacon VIII: Historie of King Henry VII. Oxford University Press.
Bacon (2012)Bacon, Francis. (2012) The Oxford Francis Bacon I: Early Writings 1584-1596. Oxford University Press.
Barker and Shugart (Eds.) (1981)Barker, Peter and Shugart, Cecil G. (Eds.). (1981) After Einstein : proceedings of the Einstein centennial celebration at Memphis State University, 14-16 March, 1979. Memphis State University Press.
Barnes, Bloor, and Henry (1996)Barnes, Barry; Bloor, David and Henry, John. (1996) Scientific Knowledge: A Sociological Analysis. University of Chicago Press.
Barseghyan (2015)Barseghyan, Hakob. (2015) The Laws of Scientific Change. Springer.
Barseghyan and Shaw (2017)Barseghyan, Hakob and Shaw, Jamie. (2017) How Can a Taxonomy of Stances Help Clarify Classical Debates on Scientific Change? Philosophies 2 (4), 24. Retrieved from http://www.mdpi.com/2409-9287/2/4/24.
Becher (1981)Becher, Tony. (1981) Towards a Definition of Disciplinary Cultures. Studies in Higher Education 6 (2), 109-122.
Bechler (1982)Bechler, Zev. (1982) Contemporary Newtonian Research (Studies in the History of Modern Science vol. 9). D. Reidel Publishing Company.
Bechtel (2008)Bechtel, William. (2008) Mental Mechanisms: Philosophical Perspectives on Cognitive Neuroscience. Lawrence Erlbaum Associates.
Bell (2009)Bell, Martin. (2009) Hume on Causation. In Norton and Taylor (2009), 147-176.
Belot (2001)Belot, Gordon. (2001) The Principle of Sufficient Reason. Journal of Philosophy 97, 55-74.
Berkeley (1957)Berkeley, George. (1957) A Treatise Concerning the Principles of Human Knowledge. Forgotten Books.
Berryman (2016)Berryman, Sylvia. (2016) Ancient Atomism. In Zalta (Ed.) (2017). Retrieved from https://plato.stanford.edu/archives/win2016/entries/atomism-ancient/https://plato.stanford.edu/archives/win2016/entries/atomism-ancient/.
Biography.com Editors (2017)Biography.com Editors. (2017) Aristotle Biography.com. Biography.com. Retrieved from https://www.biography.com/people/aristotle-9188415.
Bird (2000)Bird, Alexander. (2000) Thomas Kuhn. Princeton University Press.
Bird (2008)Bird, Alexander. (2008) The Historical Turn in the Philosophy of Science. In Psillos and Curd (Eds.) (2008), 67-77.
Bird (2011)Bird, Alexander. (2011) Thomas Kuhn. In Zalta (Ed.) (2016). Retrieved from http://plato.stanford.edu/archives/sum2016/entries/thomas-kuhn/.
Biro (2009)Biro, John. (2009) Hume's New Science of the Mind. In Norton and Taylor (2009), 40-69.
Bloor (1976)Bloor, David. (1976) Knowledge and Social Imagery. Routledge and K. Paul.
Bloor (1984)Bloor, David. (1984) Scientific rationality: The sociological turn. Springer Netherlands.
Bloor (1999)Bloor, David. (1999) Anti-Latour. Studies in History and Philosophy of Science 30 (1), 131-136.
Bodnar (2016)Bodnar, Istvan. (2016) Aristotle's Natural Philosophy. In Zalta (Ed.) (2016). Retrieved from https://plato.stanford.edu/entries/aristotle-natphil/.
Bolt (1998)Bolt, Marvin P. (1998) John Herschel's Natural Philosophy: On the Knowing of Nature and the Nature of Knowing in Early-Nineteenth-Century Britain. University of Notre Dame.
Boole (2003)Boole, George. (2003) The Laws of Thought. Buffalo: Prometheus Books.
Boyd, Gasper and Trout (Eds.) (1991)Boyd, Richard; Gasper, Philip and Trout, John D. (Eds.). (1991) The Philosophy of Science. The MIT Press.
Briggs (Ed.) (1996)Briggs, John and Peltonen, Markku. (1996) The Cambridge Companion to Bacon. Cambridge University Press.
Bristow (2011)Bristow, William. (2011) Enlightenment. In Zalta (Ed.) (2016). Retrieved from http://plato.stanford.edu/entries/enlightenment/.
Bristow (2017)Bristow, William. (2017) Enlightenment. In Zalta (Ed.) (2016). Retrieved from https://plato.stanford.edu/archives/fall2017/entries/enlightenment/.
Brown (2001)Brown, James Robert. (2001) Who Rules in Science? Harvard University Press.
Brown and Mittelstrass (Eds.) (1989)Brown, James Robert and Mittelstrass, Jürgen. (Eds.). (1989) An Intimate Relation: Studies in the History and Philosophy of Science Presented to Robert E. Butts on his 60th Birthday. Springer.
Buchdahl (1971)Buchdahl, Gerd. (1971) Inductivist Versus Deductivist Approaches in the Philosophy of Science as illustrated by some controversies between Whewell And Mill. The Monist 55 (3), 343-367. Retrieved from http://www.jstor.org/stable/27902224.
Buck and Cohen (Eds.) (1971)Buck, Roger C. and Cohen, Robert S. (Eds.). (1971) PSA 1970: In Memory of Rudolf Carnap Proceedings of the 1970 Biennial Meeting Philosophy of Science Association. Springer.
Bunge (1999)Bunge, Mario. (1999) Social Science Under Debate. University of Toronto Press.
Burkholder (2014)Burkholder, Joel. (2014) Protomethod, The Third Law, and Ethical Propositions. Unpublished manuscript.
Butterfield (1965)Butterfield, Herbert. (1965) The Whig Interpretation of History. New York: W. W. Norton.
Butts and Davis (1970)Butts, Robert and Davis, John W. (Eds.). (1970) The Methodological Heritage of Newton. University of Toronto Press.
Butts and Hintikka (Eds.) (1977)Butts, Robert and Hintikka, Jaakko. (Eds.). (1977) Historical and Philosophical Dimensions of Logic, Methodology and Philosophy of Science. Springer.
Callon, Rip, and Law (1986)Callon, Michel; Rip, Arie and Law, John. (Eds.). (1986) Mapping the Dynamics of Science and Technology. Palgrave Macmillan UK.
Cannon (1960)Cannon, Susan Faye. (1960) The Problem of Miracles in the 1830s. Victorian Studies 4 (1), 4-32.
Cannon (1961a)Cannon, Susan Faye. (1961) John Herschel and the Idea of Science. Journal of the History of Ideas 22 (2), 215-239.
Cannon (1961b)Cannon, Susan Faye. (1961) The Impact of Uniformitarianism: Two Letters from John Herschel to Charles Lyell, 1836-37. Proceedings of the American Philosophical Society 105 (3), 310-314.
Cantor and Hodge (Eds.) (1981)Cantor, Geoffery and Hodge, Michael Jonathan Sessions. (Eds.). (1981) Conceptions of Ether: Studies in the History of Ether Theories, 1740-1900. Cambridge University Press.
Carls (2016)Carls, Paul. (2016) Émile Durkheim. Internet Encyclopedia of Philosophy. Retrieved from http://www.iep.utm.edu/durkheim/.
Carnap (1934a)Carnap, Rudolf. (1934) Meaning, Assertion and Proposal. Philosophy of Science 1 (3), 359-360.
Carnap (1934b)Carnap, Rudolf. (1934) The Unity of Science. K. Paul, Trench, Trubner & Co..
Carnap (1935)Carnap, Rudolf. (1935) Philosophy and Logical Syntax. K. Paul, Trench, Trubner & Co..
Carnap (1936)Carnap, Rudolf. (1936) Testability and Meaning. Philosophy of Science 3 (4), 419-471.
Carnap (1937a)Carnap, Rudolf. (1937) Foundations of Logic and Mathematics. University of Chicago Press.
Carnap (1937b)Carnap, Rudolf. (1937) Testability and Meaning – Continued. Philosophy of Science 4 (1), 1-40.
Carnap (1937c)Carnap, Rudolf. (1937) The Logical Syntax of Language. Routledge Kegan & Paul.
Carnap (1938)Carnap, Rudolf. (1938) Empiricism and the Language of Science. Synthese 3 (12), 33-35.
Carnap (1941)Carnap, Rudolf. (1941) Studies in Semantics: Introduction to Semantics and Formalization of Logic. Oxford University Press.
Carnap (1942)Carnap, Rudolf. (1942) Introduction to Semantics. Harvard University Press.
Carnap (1945a)Carnap, Rudolf. (1945) Hall and Bergmann on Semantics. Mind 54 (214), 148-155.
Carnap (1945b)Carnap, Rudolf. (1945) On Inductive Logic. Philosophy of Science 12 (2), 72-97.
Carnap (1945c)Carnap, Rudolf. (1945) The Two Concepts of Probability: The Problem of Probability. Philosophy and Phenomenological Research 5 (4), 513-532.
Carnap (1946a)Carnap, Rudolf. (1946) Formalization of Logic. Harvard University Press.
Carnap (1946b)Carnap, Rudolf. (1946) Introduction to Semantics. Harvard University Press.
Carnap (1946c)Carnap, Rudolf. (1946) Modalities and Quantification. The Journal of Symbolic Logic 11 (2), 33-64.
Carnap (1946d)Carnap, Rudolf. (1946) Rejoinder to Mr. Kaufmann's Reply. Philosophy and Phenomenological Research 6 (4), 609-611.
Carnap (1946e)Carnap, Rudolf. (1946) Remarks on Induction and Truth. Philosophy and Phenomenological Research 6 (4), 590-602.
Carnap (1946f)Carnap, Rudolf. (1946) Theory and Prediction in Science. Science 104 (2710), 520-521.
Carnap (1947a)Carnap, Rudolf. (1947) Formalization of Logic. Harvard University Press.
Carnap (1947b)Carnap, Rudolf. (1947) On the Application of Inductive Logic. Philosophy and Phenomenological Research 8 (1), 133-148.
Carnap (1948a)Carnap, Rudolf. (1948) Introduction to Semantics. Harvard University Press.
Carnap (1948b)Carnap, Rudolf. (1948) Probability as a Guide in Life. ETC: A Review of General Semantics 5 (4), 263-267.
Carnap (1948c)Carnap, Rudolf. (1948) Reply to Nelson Goodman. Philosophy and Phenomenological Research 8 (3), 461-462.
Carnap (1948d)Carnap, Rudolf. (1948) Rudolf Carnap's Analysis of `Truth': Reply. Philosophy and Phenomenological Research 9 (2), 300-304.
Carnap (1949)Carnap, Rudolf. (1949) A Reply to Leonard Linsky. Philosophy of Science 16 (4), 347-350.
Carnap (1950a)Carnap, Rudolf. (1950) Empiricism, Semantics, and Ontology. Revue Internationale de Philosophie 4 (11), 20-40.
Carnap (1950b)Carnap, Rudolf. (1950) Logical Foundations of Probability. Routledge Kegan & Paul.
Carnap (1950c)Carnap, Rudolf. (1950) Rejoinder to Linsky. Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition 1 (6), 83.
Carnap (1951a)Carnap, Rudolf. (1951) On Some Concepts of Pragmatics. Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition 6 (6), 89-91.
Carnap (1951b)Carnap, Rudolf. (1951) The Logical Syntax of Language. The Humanities Press.
Carnap (1951c)Carnap, Rudolf. (1951) The Nature and Application of Inductive Logic: Consisting of six sections from Logical Foundations of Probability. University of Chicago Press.
Carnap (1951d)Carnap, Rudolf. (1951) University of Chicago Press. Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition 2 (5), 75-80.
Carnap (1952a)Carnap, Rudolf. (1952) Empiricism, Semantics, and Ontology. In Linsky (Ed.) (1952), 208-228.
Carnap (1952b)Carnap, Rudolf. (1952) Meaning Postulates. Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition 3 (5), 65-73.
Carnap (1952c)Carnap, Rudolf. (1952) The Continuum of Inductive Methods. University of Chicago Press.
Carnap (1953a)Carnap, Rudolf. (1953) Inductive Logic and Science. Proceedings of the American Academy of Arts and Sciences 80 (3), 189-197.
Carnap (1953b)Carnap, Rudolf. (1953) On the Comparative Concept of Confirmation. The British Journal for the Philosophy of Science 3 (12), 311-318.
Carnap (1953c)Carnap, Rudolf. (1953) Remarks to Kemeny's Paper. Philosophy and Phenomenological Research 13 (3), 375-376.
Carnap (1953d)Carnap, Rudolf. (1953) What Is Probability? Scientific American 189 (3), 128-139.
Carnap (1955a)Carnap, Rudolf. (1955) Foundations of Logic and Mathematics. In Neurath, Carnap and Morris (Eds.) (1955).
Carnap (1955b)Carnap, Rudolf. (1955) Meaning and Synonymy in Natural Languages. Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition 6 (3), 33-47.
Carnap (1956a)Carnap, Rudolf. (1956) Empiricism, Semantics, and Ontology. University of Chicago Press.
Carnap (1956b)Carnap, Rudolf. (1956) Meaning and Necessity: A Study in Semantics and Modal Logic. University of Chicago Press.
Carnap (1956c)Carnap, Rudolf. (1956) Remarks on Popper's Note on Content and Degree of Confirmation. The British Journal for the Philosophy of Science 7 (21), 243-244.
Carnap (1956d)Carnap, Rudolf. (1956) The Methodological Character of Theoretical Concepts. In Feigl, Scriven and Maxwell (Eds.) (1956), 38-75.
Carnap (1958)Carnap, Rudolf. (1958) Introduction to Symbolic Logic and Its Applications. Dover Publications.
Carnap (1959a)Carnap, Rudolf. (1959) Introduction to Semantics and Formalization of Logic. Harvard University Press.
Carnap (1959b)Carnap, Rudolf. (1959) The Logical Syntax of Language. Littlefield, Adams & Co..
Carnap (1961)Carnap, Rudolf. (1961) Introduction to Semantics and Formalization of Logic. Harvard University Press.
Carnap (1962)Carnap, Rudolf. (1962) Logical Foundations of Probability. University of Chicago Press.
Carnap (1963a)Carnap, Rudolf. (1963) Discussion: Variety, Analogy, and Inductive Logic. Philosophy of Science 30 (3), 222-227.
Carnap (1963b)Carnap, Rudolf. (1963) Replies and Systematic Expositions. In Schilpp (Ed.) (1963), 859-1013.
Carnap (1963c)Carnap, Rudolf. (1963) Intellectual Autobiography. In Schilpp (Ed.) (1963), 3-86.
Carnap (1967a)Carnap, Rudolf. (1967) The Logical Structure of the World and Pseudoproblems in Philosophy. University of California Press.
Carnap (1967b)Carnap, Rudolf. (1967) The Logical Structure of the World and Pseudoproblems in Philosophy. Routledge & Kegan Paul PLC.
Carnap (1968)Carnap, Rudolf. (1968) Introduction to Semantics and Formalization of Logic. Harvard University Press.
Carnap (1970)Carnap, Rudolf. (1970) Empiricism, Semantics, and Ontology. In Linsky (Ed.) (1970), 208-231.
Carnap (1971a)Carnap, Rudolf. (1971) Foundations of Logic and Mathematics. In Neurath, Carnap and Morris (Eds.) (1971).
Carnap (1971b)Carnap, Rudolf. (1971) The Logical Syntax of Language. Routledge Kegan & Paul.
Carnap (1973)Carnap, Rudolf. (1973) Notes on Probability and Induction. Synthese 25 (3/4), 269-298.
Carnap (1975a)Carnap, Rudolf. (1975) Introduction to Semantics and Formalization of Logic. Harvard University Press.
Carnap (1975b)Carnap, Rudolf. (1975) Observation Language and Theoretical Language. In Hintikka (Ed.) (1975).
Carnap (1979)Carnap, Rudolf. (1979) Philosophy and Logical Syntax. AMS Press.
Carnap (1983)Carnap, Rudolf. (1983) The Logical Structure of the World and Pseudoproblems in Philosophy. University of California Press.
Carnap (1984)Carnap, Rudolf. (1984) On the Character of Philosophic Problems. Philosophy of Science 51 (1), 5-19.
Carnap (1987)Carnap, Rudolf. (1987) On Protocol Sentences. Noûs 21 (4), 457-470.
Carnap (1988)Carnap, Rudolf. (1988) Meaning and Necessity: A Study in Semantics and Modal Logic. University of Chicago Press.
Carnap (1991)Carnap, Rudolf. (1991) Logical Foundations of the Unity of Science. In Boyd, Gasper and Trout (Eds.) (1991), 393-404.
Carnap (1995)Carnap, Rudolf. (1995) An Introduction to the Philosophy of Science. Dover Publications.
Carnap (1997a)Carnap, Rudolf. (1997) Philosophy and Logical Syntax. Thoemmes Press.
Carnap (1997b)Carnap, Rudolf. (1997) The Unity of Science. Thoemmes Press.
Carnap (2001)Carnap, Rudolf. (2001) Logical Syntax of Language. Routledge Kegan & Paul.
Carnap (2002)Carnap, Rudolf. (2002) The Logical Syntax of Language. Open Court.
Carnap (2003a)Carnap, Rudolf. (2003) Introduction to Symbolic Logic and Its Applications. Dover Publications.
Carnap (2003b)Carnap, Rudolf. (2003) The Logical Structure of the World and Pseudoproblems in Philosophy. Open Court.
Carnap (2006)Carnap, Rudolf. (2006) Introduction to Semantics and Formalization of Logic. Harvard University Press.
Carnap (2007)Carnap, Rudolf. (2007) Meaning and Necessity: A Study in Semantics and Modal Logic. Clarke Press.
Carnap (2008)Carnap, Rudolf. (2008) Meaning and Necessity: A Study in Semantics and Modal Logic. Clarke Press.
Carnap (2010)Carnap, Rudolf. (2010) Logical Syntax of Language (The International Library of Philosophy: Philosophy of Mind and Language). Routledge Kegan & Paul.
Carnap (2011a)Carnap, Rudolf. (2011) Introduction to Symbolic Logic and Its Applications. Dover Publications.
Carnap (2011b)Carnap, Rudolf. (2011) The Unity of Science. Routledge.
Carnap (2012)Carnap, Rudolf. (2012) The Unity of Science. Routledge.
Carnap (2017a)Carnap, Rudolf. (2017) Introduction to Semantics and Formalization of Logic. Harvard University Press.
Carnap (2017b)Carnap, Rudolf. (2017) Value Concepts (1958). Synthese 194 (1), 185-194.
Carnap and Bar-Hillel (1938)Carnap, Rudolf and Bar-Hillel, Yehoshua. (1938) Semantic Information. The British Journal for the Philosophy of Science 4 (14), 147-157.
Carnap and Shimony (1977)Carnap, Rudolf and Shimony, Abner. (1977) Two Essays on Entropy. University of California Press.
Carnap et al. (1937)Carnap, Rudolf et al. (1937) International Encyclopedia of Unified Science. Science 86 (2235), 400-401.
Carnielli and Marcos (2001)Carnielli, Walter and Marcos, Joano. (2001) Ex Contradictione Non Sequitur Quodlibet. Bulletin of Advanced Reasoning and Knowledge 1, 89-109.
Carruthers, Stitch, and Siegal (Eds.) (2002)Carruthers, Peter; Stitch, Stephen and Siegal, Michael. (Eds.). (2002) The Cognitive Basis of Science. Cambridge University Press.
Cat (2014)Cat, Jordi. (2014) Unity of Science. In Zalta (Ed.) (2016). Retrieved from http://plato.stanford.edu/entries/scientific-unity/.
Cat (2017)Cat, Jordi. (2017) Otto Neurath. In Zalta (Ed.) (2016). Retrieved from https://plato.stanford.edu/archives/win2017/entries/neurath/.
Chalmers (1996)Chalmers, David. (1996) The Conscious Mind: In Search of a Fundamental Theory. Oxford University Press.
Chalmers (2013)Chalmers, Alan. (2013) What is This Thing Called Science? University of Queensland Press.
Chalmers (2014)Chalmers, Alan. (2014) Atomism from the 17th to the 20th Century. In Zalta (Ed.) (2016). Retrieved from http://plato.stanford.edu/archives/win2014/entries/atomism-modern/.
Chang (2004)Chang, Hasok. (2004) Inventing Temperature: Measurement and Scientific Progress. Oxford University Press.
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1. Introductory Remarks

While it is in the nature of philosophical movements and their leading doctrines to court controversy, the Vienna Circle and its philosophies did so more than most. To begin with, its members styled themselves as conceptual revolutionaries who cleared the stables of academic philosophy by showing metaphysics not simply to be false, but to be cognitively empty and meaningless. In addition, they often associated their attempt to overcome metaphysics with their public engagement for scientific Enlightenment reason in the ever-darkening political situation of 1920s and 1930s central Europe. Small wonder then that the Vienna Circle has sharply divided opinion from the start. There is very little beyond the basic facts of membership and its record of publications and conferences that can be asserted about it without courting some degree of controversy. (For English-language survey monographs and articles on the Vienna Circle, see Kraft 1950, Jorgensen 1951, Ayer 1959b, Passmore 1967, Hanfling 1981, Stadler 1998, Richardson 2003. Particularly rich in background and bio-bibliographical materials is Stadler 1997 [2001]. The best short introductory book has remained untranslated: Haller 1993.)

Fortunately, more than three decades worth of recent scholarship in history of philosophy of science now allows at least some disputes to be put into perspective. (See, e.g., the following at least in part English-language collections of articles and research monographs: Haller 1982, McGuinness 1985, Rescher 1985, Gower 1987, Proust 1989, Zolo 1989, Coffa 1991, Spohn 1991, Uebel 1991, Bell and Vossenkuhl 1992, Sarkar 1992, Uebel 1992, Oberdan 1993, Stadler 1993, Cirera 1994, Salmon and Wolters 1994, Cartwright, Cat, Fleck and Uebel 1996, Giere and Richardson 1996, Nemeth and Stadler 1996, Sarkar 1996, Richardson 1998, Friedman 1999, Wolenski and Köhler 1999, Fetzer 2000, Friedman 2000, Bonk 2003, Hardcastle and Richardson 2003, Parrini, Salmon and Salmon 2003, Stadler 2003, Awodey and Klein 2004, Reisch 2005, Galavotti 2006, Carus 2007, Creath and Friedman 2007, Nemeth, Schmitz and Uebel 2007, Richardson and Uebel 2007, Uebel 2007, Wagner 2009, Manninen and Stadler 2010, McGuinness 2011, Symons, Pombo and Torres 2011, Creath 2012, and Wagner 2012, Damböck 2016, Schiemer 2016.) What distinguishes these works from valuable collections like Schilpp 1963, Hintikka 1975 and Achinstein and Barker 1979 is that the unspoken assumption, to have understood Vienna Circle philosophy correctly enough so as to consider its consequences straightforward, is implicitly questioned in the more recent scholarship. Many other pieces of new Vienna Circle scholarship are spread throughout philosophical journals and essay collections with more systematic or wider historical scope; important work has also been done in German, Italian and French language publications but here must remain unreferenced.)

Two facts must be clearly recognized if a proper evaluation of the Vienna Circle is to be attempted. The first is, that, despite its relatively short existence, even some of the most central theses of the Vienna Circle underwent radical changes. The second is that its members were by no means of one mind in all important matters; occasionally they espoused perspectives so radically at variance with each other that even their ostensive agreements cannot remain wholly unquestioned. Behind the rather thin public front, then, quite different philosophical projects were being pursued by the leading participants with, moreover, changing alliances. One way of taking account of this is by speaking (as above) explicitly of the philosophies (in the plural) of the Vienna Circle (and to avoid the singular definite description) while using the expression “Vienna Circle philosophy” (without an article) in a neutral generic sense.

Recent scholarship has provided what the received view of Viennese neopositivism lacks: recognition and documentation of the sometimes sharply differentiated positions behind the generic surface. This does not invalidate all previous scholarship, including some fundamental criticisms of its positions, but it restores a depth to Vienna Circle philosophy that was absent from the standard histories. The value of this development must not be underestimated, for the recognition of the Vienna Circle’s sophisticated engagement with aspects of the philosophical tradition and contemporaneous challenges calls into question unwarranted certainties of our own self-consciously post-positivist era. While there remains support for the view that philosophical doctrines were held in the Vienna Circle that wholly merited many of the standard criticisms to be cited below, there is now also support for the view that in nearly all such cases, these doctrines were already in their day opposed within the Circle itself. While some of the Vienna Circle philosophies are dated and may even be, as John Passmore once put it, as dead as philosophies can be, others show signs of surprising virulence. Which ones these are, however, remains a matter of debate.

The lead pursued in this article is provided by the comments of a long-time associate of the Vienna Circle, C.G. Hempel, made in 1991:

When people these days talk about logical positivism or the Vienna Circle and say that its ideas are passé, this is just wrong. This overlooks the fact that there were two quite different schools of logical empiricism, namely the one of Carnap and Schlick and so on and then the quite different one of Otto Neurath, who advocates a completely pragmatic conception of the philosophy of science…. And this form of empiricism is in no way affected by any of the fundamental objections against logical positivism…. (quoted in Wolters 2003, 117)

Without setting out to endorse Hempel’s specific claim about how the two schools divide, the aim here is to fill out his suggestive picture by indicating what Schlick, Carnap and Neurath stand for philosophically and why the different wings of the Vienna Circle require differentiated assessments. After reviewing the basic facts and providing an overall outline of Vienna Circle philosophy (in sect. 2), this article considers various doctrines in greater detail by way of discussing standard criticisms with the appropriate distinctions in mind (in sect. 3). No comprehensive assessment of the Vienna Circle and the work of its members can be attempted here, but some basic conclusions will be drawn (in sect. 4).

2. The Basics: People, Activities and Overview of Doctrines

2.1 People

The Vienna Circle was a group of scientifically trained philosophers and philosophically interested scientists who met under the (nominal) leadership of Moritz Schlick for often weekly discussions of problems in the philosophy of science during academic terms in the years from 1924 to 1936. As is not uncommon with such groups, its identity is blurred along several edges. Not all of those who ever attended the discussions can be called members, and not all who attended did so over the entire period. Typically, attention is focused on long-term regulars who gained prominence through their philosophical publications, but even these do not in all cases fall into the period of the Vienna Circle proper. It is natural, nevertheless, to consider under the heading “Vienna Circle” also the later work of leading members who were still active in the 1940s, 50s and 60s. Finally, there is the so-called periphery of international contacts and visitors that prefigured the post-World War II network of analytical philosophers of science. In the present article the emphasis will be placed on the long-term regulars whose contributions will be followed, selectively, into the post-Schlick era.

According to its unofficial manifesto (see section 2.3 below), the Circle had “members” and recognized others as “sympathetic” to its aims. It included as members, besides Schlick who had been appointed to Mach’s old chair in Philosophy of the Inductive Sciences at the University of Vienna in 1922, the mathematician Hans Hahn, the physicist Philipp Frank, the social scientist Otto Neurath, his wife, the mathematician Olga Hahn-Neurath, the philosopher Viktor Kraft, the mathematicians Theodor Radacovic and Gustav Bergmann and, since 1926, the philosopher and logician Rudolf Carnap. (Even before World War I, there existed a similarly oriented discussion circle that included Frank, Hahn and Neurath. During the time of the Schlick Circle, Frank resided in Prague throughout, Carnap did so from 1931.) Further members were recruited among Schlick’s students, like Friedrich Waismann, Herbert Feigl and Marcel Natkin, others were recruited among Hahn’s students, like Karl Menger and Kurt Gödel. Though listed as members in the manifesto, Menger and Kraft later wanted to be known only as as sympathetic associates, like, all along, the mathematician Kurt Reidemeister and the philosopher and historian of science Edgar Zilsel. (Karl Popper was never a member or associate of the Circle, though he studied with Hahn in the 1920s and in the early 1930s discussed its doctrines with Feigl and Carnap.) Over the years, other participants (not listed in the manifesto) included other students of Schlick’s and Hahn’s like Bela von Juhos, Josef Schächter, Walter Hollitscher, Heinrich Neider, Rose Rand, Josef Rauscher and Käthe Steinhardt, a secondary teacher, Robert Neumann, and, as notable thinkers with independent connections, the jurist and philosopher Felix Kaufmann (also a member of F.A. von Hayek’s “Geistkreis”) and the innovative psychologist Egon Brunswik (coming, like the even more loosely associated sociologists Paul Lazarsfeld and Marie Jahoda, from the pioneering Karl Bühler’s University Institute of Psychology).

Despite its prominent position in the rich, if fragile, intellectual culture of inter-war Vienna and most likely due to its radical doctrines, the Vienna Circle found itself virtually isolated in most of German speaking philosophy. The one exception was its contact and cooperation with the Berlin Society for Empirical (later: Scientific) Philosophy (the other point of origin of logical empiricism). The members of the Berlin Society sported a broadly similar outlook and included, besides the philosopher Hans Reichenbach, the logicians Kurt Grelling and Walter Dubislav, the psychologist Kurt Lewin, the surgeon Friedrich Kraus and the mathematician Richard von Mises. (Its leading members Reichenbach, Grelling and Dubislav were listed in the Circle’s manifesto as sympathisers.) At the same time, members of the Vienna Circle also engaged directly, if selectively, with the Warsaw logicians (Tarski visited Vienna in 1930, Carnap later that year visited Warsaw and Tarski returned to Vienna in 1935). Probably partly because of its firebrand reputation, the Circle attracted also a series of visiting younger researchers and students including Carl Gustav Hempel from Berlin, Hasso Härlen from Stuttgart, Ludovico Geymonat from Italy, Jørgen Jørgensen, Eino Kaila, Arne Naess and Ake Petzall from Scandinavia, A.J. Ayer from the UK, Albert Blumberg, Charles Morris, Ernest Nagel and W.V.O. Quine from the USA, H.A. Lindemann from Argentina and Tscha Hung from China. (The reports and recollections of these former visitors—e.g. Nagel 1936—are of interest in complementing the Circle’s in-house histories and recollections which start with the unofficial manifesto—Carnap, Hahn and Neurath 1929—and extend through Neurath 1936, Frank 1941, 1949a and Feigl 1943 to the memoirs by Carnap 1963, Feigl 1969a, 1969b, Bergmann 1987, Menger 1994.)

The aforementioned social and political engagement of members of the Vienna Circle and of Vienna Circle philosophy for Enlightenment reason had never made the advancement of its associates or protegées easy in Viennese academia. From 1934 onwards, with anti-semitism institutionalized and irrationalism increasingly dominating public discourse, this engagement began to cost the Circle still more dearly. Not only was the Verein Ernst Mach closed down early that year for political reasons, but the ongoing dispersal of Circle members by emigration, forced exile and death meant that after the murder of Schlick in 1936 only a small rump was able to continue meetings for another two years in Vienna. (1931: Feigl emigrated to USA; 1934: Hahn died, Neurath fled to Holland, 1940 to UK; 1935: Carnap emigrated to USA; 1936: Schlick murdered; 1937: Menger emigrated to USA, Waismann to UK; 1938: Frank, Kaufmann, Brunswik, Bergmann emigrated to USA; Zilsel, Rand to UK, later to USA; Hollitscher fled to Switzerland, later to UK; Schächter emigrated to Palestine; 1940: Gödel emigrated to USA; see Dahms 1995 for a chronology of the exodus.) But the end of the Vienna Circle as such did not mean the end of its influence due to the continuing development of the philosophy of former members (and the work of Kraft in post-World War II Vienna; on this see Stadler 2008). Particularly through their work in American exile (esp. Carnap at Harvard, Chicago and UCLA; Feigl at Iowa and Minnesota; less so Frank at Harvard) and that of earlier American visitors (esp. Quine, Nagel), as well as through the work of fellow emigrées from the Berlin Society (esp. Reichenbach, Hempel) and their students (Hilary Putnam, Wesley Salmon), logical empiricism strongly influenced the post-World War II development of analytic philosophy of science. By contrast, Waismann had little influence in the UK where Neurath, already marginalized, had died in 1945. (The full story of logical empiricism’s acculturation in the English speaking world remains to be written, but see Howard 2003, Reisch 2005, Uebel 2005a, 2010, and Douglas 2009 for considerations of aspects of Vienna Circle philosophy that were neglected in the process and remained long forgotten.)

2.2 Activities

After its formative phase which was confined to the Thursday evening discussions, the Circle went public in 1928 and 1929 when it seemed that the time had come for their emerging philosophy to play a distinctive role not only in the academic but also the public sphere. In November 1928, at its founding session, Schlick accepted the presidency of the newly formed Verein Ernst Mach (Association Ernst Mach), Hahn accepted one of its vice-presidencies and Neurath and Carnap joined its secretariat. Originally proposed by the Austrian Freidenkerbund (Free Thinker Association), the Verein Ernst Mach was dedicated to the dissemination of scientific ways of thought and so provided a forum for popular lectures on the new scientific philosophy. In the following year the Circle stepped out under its own name (invented by Neurath) with a manifesto and a special conference. The publication of “The Scientific World Conception: The Vienna Circle”, signed by Carnap, Hahn and Neurath and dedicated to Schlick, coincided with the “First Conference for the Epistemology of the Exact Sciences” in mid-September 1929, organised jointly with the Berlin Society as an adjunct to the Fifth Congress of German Physicists and Mathematicians in Prague (where Frank played a prominent role in the local organising committee). (On the production history and early reception of the manifesto see Uebel 2008.) A distinct philosophical school appeared to be emerging, one that was dedicated to ending the previous disputes of philosophical schools by dismissing them, controversially, as strictly speaking meaningless.

Throughout the early and mid-1930s the Circle kept a high and increasingly international profile with its numerous publications and conferences. In 1930, the Circle took over, again together with the Berlin Society, the journal Annalen der Philosophie and restarted it under the name of Erkenntnis with Carnap and Reichenbach as co-editors. (Besides publishing original articles and sustaining lengthy debates, this journal featured selected proceedings of their early conferences and documented the lecture series of the Verein Ernst Mach and the Berlin Society as well as their international congresses.) In addition, from 1928 until 1936, Schlick and Frank served as editors of their book series “Schriften zur wissenschaftlichen Weltauffassung” (“Writings on the Scientific World Conception”), which published major works by leading members and early critics like Karl Popper, while Neurath served, from 1933 until 1939, as editor of the series “Einheitswissenschaft” (“Unified Science”), which published more introductory essays by leading members and sympathisers. Conference-wise, the Circle organized, again with the Berlin Society, a “Second Conference for the Epistemology of the Exact Sciences” as an adjunct to the Sixth Congress of German Physicists and Mathematicians in Königsberg in September 1930 (where Reidemeister played a prominent role in the organization and Gödel first announced his incompleteness result in the discussion) and then began the series of International Congresses on the Unity of Science with a “Pre-Conference” just prior to the start of the Eighth International Congress of Philosophy in Prague in September 1934. This, their last conference in Central Europe, was followed by the International Congresses of various sizes in Paris (September 1935, July 1937), Copenhagen (June 1936), Cambridge, England (July 1938), Cambridge, Mass. (September 1939), all in the main organized by Neurath; a smaller last gathering was held in Chicago in September 1941. By 1938 their collective publication activity began to centre on a monumentally planned International Encyclopedia of Unified Science, with Neurath as editor-in-chief and Carnap and Charles Morris as co-editors; by the time of Neurath’s death in 1945, only 10 monographs had appeared and the series was wound up in 1970 numbering 20 monographs under the title “Foundations of the Unity of Science” (notably containing Thomas Kuhn’s Structure of Scientific Revolutions amongst them).

Individually, the members of the Vienna Circle published extensively before, during and after the years of the Circle around Schlick. For some (Frank, Hahn, Menger, Neurath), philosophy was only part of their scientific output, with numerous monographs and articles in their respective disciplines (mathematics, physics and social science); others (Schlick, Carnap, Feigl, Waismann) concentrated on philosophy, but even their output cared relatively little for traditional concerns of the field. Here it must be noted that two early monographs by Schlick (1918/25) and Carnap (1928a), commonly associated with the Vienna Circle, mostly predate their authors’ participation there and exhibit a variety of influences not typically associated with logical positivism (see section 3.7 below). Moreover, important monographs by Frank (1932), Neurath (1931a), Carnap (1934/37) and Menger (1934) in the first half of the 1930s represent moves away from positions that had been held in the Circle before and contradict its orthodox profile. Yet the Circle’s orthodoxy, as it were, is not easily pinned down either. Schlick himself was critical of the manifesto of 1929 and gave a brief vision statement of his own in “The Turning Point in Philosophy” (1930). A long-planned book by Waismann of updates on Wittgenstein’s thought, to which Schlick was extremely sympathetic, was never completed as originally planned and only appeared posthumously (Waismann 1965; for earlier material see Baker 2003). Comparison with rough transcripts of the Circle’s discussions in the early 1930s (for transcripts from between December 1930 and July 1931 see Stadler 1997 [2001, 241–299]) suggest that Waismann’s Wittgensteinian “Theses” (Waismann 1967 [1979, Appendix B]) come closest to an elaboration of the orthodox Circle position at that time (but which remained not undisputed even then). Again, what needs to be stressed is that all of the Circle’s publications are to be understood as contributions to ongoing discussions among its members and associates.

2.3 Overview of Doctrines

Despite the pluralism of the Vienna Circle’s views, there did exist a minimal consensus which may be put as follows. A theory of scientific knowledge was propagated which sought to renew empiricism by freeing it from the impossible task of justifying the claims of the formal sciences. It will be noted that this updating did not leave empiricism unchanged.

Following the logicism of Frege and Russell, the Circle considered logic and mathematics to be analytic in nature. Extending Wittgenstein’s insight about logical truths to mathematical ones as well, the Circle considered both to be tautological. Like true statements of logic, mathematical statements did not express factual truths: devoid of empirical content they only concerned ways of representing the world, spelling out implication relations between statements. The knowledge claims of logic and mathematics gained their justification on purely formal grounds, by proof of their derivability by stated rules from stated axioms and premises. (Depending on the standing of these axioms and premises, justification was conditional or unconditional.) Thus defanged of appeals to rational intuition, the contribution of pure reason to human knowledge (in the form of logic and mathematics) was thought easily integrated into the empiricist framework. (Carnap sought to accommodate Gödel’s incompleteness results by separating analyticity from effective provability and by postulating that arithmetic consisted of an infinite series of ever richer arithmetical languages; see the discussion and references in section 3.2 below.)

The synthetic statements of the empirical sciences meanwhile were held to be cognitively meaningful if and only if they were empirically testable in some sense. They derived their justification as knowledge claims from successful tests. Here the Circle appealed to a meaning criterion the correct formulation of which was problematical and much debated (and will be discussed in greater detail in section 3.1 below). Roughly, if synthetic statements failed testability in principle they were considered to be cognitively meaningless and to give rise only to pseudo-problems. No third category of significance besides that of a priori analytical and a posteriori synthetic statements was admitted: in particular, Kant’s synthetic a priori was banned as having been refuted by the progress of science itself. (The theory of relativity showed what had been held to be an example of the synthetic a priori, namely Euclidean geometry, to be false as the geometry of physical space.) Thus the Circle rejected the knowledge claims of metaphysics as being neither analytic and a priori nor empirical and synthetic. (On related but different grounds, they also rejected the knowledge claims of normative ethics: whereas conditional norms could be grounded in means-ends relations, unconditional norms remained unprovable in empirical terms and so depended crucially on the disputed substantive a priori intuition.)

Given their empiricism, all of the members of the Vienna Circle also called into question the principled separation of the natural and the human sciences. They were happy enough to admit to differences in their object domains, but denied the categorical difference in both their overarching methodologies and ultimate goals in inquiry, which the historicist tradition in the still only emerging social sciences and the idealist tradition in philosophy insisted on. The Circle’s own methodologically monist position was sometimes represented under the heading of “unified science”. Precisely how such a unification of the sciences was to be effected or understood remained a matter for further discussion (see section 3.3 below).

It is easy to see that, combined with the rejection of rational intuition, the Vienna Circle’s exclusive apportionment of reason into either formal a priori reasoning, issuing in analytic truths (or contradictions), and substantive a posteriori reasoning, issuing in synthetic truths (or falsehoods), severely challenged the traditional understanding of philosophy. All members of the Circle hailed the end of distinctive philosophical system building. In line with the Tractatus claim that all philosophy is really a critique of language, the Vienna Circle took the so-called linguistic turn, the turn to representation as the proper subject matter of philosophy. Philosophy itself was denied a separate first-order domain of expertise and declared a second-order inquiry. Whether the once queen of the sciences was thereby reduced to the mere handmaiden of the latter was still left open. It remained a matter of disagreement whether philosophy was also denied wholly autonomous sources of insight and what type of distinctively philosophical insight, if any, would remain legitimate. Just as importantly, the tools of modern logic were employed also for metatheoretical construction, not just for the reduction of empirical claims to their observational base or, more generally, for the derivation of their observational consequences. For the price of abandoning foundationalist certainty this allowed for an enormous expansion of the domain of empirical discourse. Ultimately, it opened the space for the still ongoing discussions of scientific realism and its alternatives (see section 3.4 below).

The Circle’s leading protagonists differed in how they conceptualized this reflexive second-order inquiry that the linguistic turn had inaugurated. Nevertheless, they all agreed broadly that the ways of representing the world were largely determined by convention. A multitude of ideas hide behind this invocation of conventionality. One particularly radical one is the denial of the apodicity of all apriority, the denial of the claim that knowledge justified through reason alone represents truths that are unconditionally necessary. Another one is the imputation of agency in the construction of the logico-linguistic frameworks that make human cognition possible, the denial that conventionality could only mean acquiescence in tradition. Whether such ideas were followed by individual members of the Circle, however, depended on their own interests and influences. It is these often overlooked or misunderstood differences that hold the key to understanding the interplay of occasionally incompatible positions that make up Vienna Circle philosophy. (As can be seen from some of their internal disputes, moreover, these differences were also not always obvious to the protagonists themselves.)

To see a striking example, consider their overarching conceptions of philosophy itself. Some protagonists retained the idea that philosophy possessed a separate disciplinary identity from science and, like Schlick, turned philosophy into a distinctive, albeit non-formal activity of meaning determination. Others, like Carnap, agreed on the distinction between philosophy and science but turned philosophy into a purely formal enterprise, the so-called logic of science. Still others went even further and, like Neurath under the banner of “unified science”, also rejected philosophy as a separate discipline and apportioned what remained of it after the rejection of metaphysics to science as its meta-theory. With Schlick, then, philosophy became the activity of achieving a much clarified and deepened understanding of the cognitive and linguistic practices actually already employed in science and everyday discourse. By contrast, for Carnap, philosophy investigated and reconstructed existing language fragments, developed new logico-linguistic frameworks and suggested possible formal conventions for science, while, for Neurath, the investigation of science was pursued by an interdisciplinary meta-theory that encompassed empirical disciplines, again with a pragmatic orientation. Thus we find in apparent competition different conceptions of post-metaphysical philosophy: the projects of experiential meaning determination, of formal rational reconstruction and of naturalistic explications of leading theoretical and methodological notions. (For roughly representative early essay-length statements of their positions see Schlick 1930, Carnap 1932a and Neurath 1932a; later restatements are given in Schlick 1937, Carnap 1936b and Neurath 1936b.) In the more detailed discussions below these differences of overall approach will figure repeatedly (see also section 3.6 below).

Criticisms of the basic positions adopted in the Vienna Circle are legion, though it may be questioned whether most of them took account of the sophisticated variations on offer. (Sometimes the Circle’s own writings are disregarded altogether and “logical positivism” is discussed only via the proxy of Ayer’s popular exposition; see, e.g., Soames 2003.) But some Neo-Kantians like Ernst Cassirer may claim that they too accepted developments like the merely relative a priori and an appropriate conception of the historical development of science. Likewise, Wittgensteinians may claim that Wittgenstein’s own opposition to metaphysics only concerned false attempts to render it intelligible: his merely ineffable but uneliminated metaphysics concerned precisely what for him were essentials of ways of representing the world. The commonest criticisms, however, concerned not the uniqueness of the Vienna Circle’s doctrines, or their faithfulness to their supposed sources, but whether they were tenable at all. Prominent objects of this type of criticism include the verificationist theory of meaning and its claimed anti-metaphysical and non-cognitivist consequences as well as its own significance; the reductionism in phenomenalist or physicalist guises that appeared to attend the Circle’s attempted operationalisation of the logical atomism of Russell and Wittgenstein; and the Circle’s alleged scientism in general and their formalist and a-historical conception of scientific cognition in particular. These criticisms are discussed in some detail below in order to assess why which of the associated doctrines remain of what importance.

As noted, the Vienna Circle did not last long: its philosophical revolution came at a cost. Yet what was so socially, indeed politically, explosive about what appears on first sight to be a particularly arid, if not astringent, doctrine of specialist scientific knowledge? To a large part, precisely what made it so controversial philosophically: its claim to refute opponents not by proving their statements to be false but by showing them to be (cognitively) meaningless. Whatever the niceties of their philosophical argument here, the socio-political impact of the Vienna Circle’s philosophies of science was obvious and profound. All of them opposed the increasing groundswell of radically mistaken, indeed irrational, ways of thinking about thought and its place in the world. In their time and place, the mere demand that public discourse be perspicuous, in particular, that reasoning be valid and premises true—a demand implicit in their general ideal of reason—placed them in the middle of crucial socio-political struggles. Some members and sympathisers of the Circle also actively opposed the then increasingly popular völkisch supra-individual holism in social science as a dangerous intellectual aberration. Not only did such ideas support racism and fascism in politics, but such ideas themselves were supported only by radically mistaken arguments concerning the nature and explanation of organic and unorganic matter. So the first thing that made all of the Vienna Circle philosophies politically relevant was the contingent fact that in their day much political discourse exhibited striking epistemic deficits. That some of the members of the Circle went, without logical blunders, still further by arguing that socio-political considerations can play a legitimate role in some instances of theory choice due to underdetermination is yet another matter. This particular issue will not be pursued further here (see references at the end of section 2.1 above), nor will the general topic of the Circle’s embedding in modernism and the discourse of modernity (see Putnam 1981b for a reductionist, Galison 1990 for a foundationalist, Uebel 1996 for a constructivist reading of their modernism, Dahms 2004 for an account of personal relations with representatives of modernism in art and architecture), will not be pursued further.

3. Selected Doctrines and their Criticisms

Given only the outlines of Vienna Circle philosophy, its controversial character is evident. The boldness of its claims made it attractive but that boldness also seemed to be its undoing. Turning to the questions of how far and, if at all, which forms of Vienna Circle philosophy stand up to some common criticisms, both the synchronic variations and the diachronic trajectories of its variants must be taken into account. This will be attempted in the sections below.

Before expectations are raised too high, however, it must also remembered that in this article only the views of members of the Vienna Circle can be discussed, even though the problematic issues were pervasive in logical empiricism generally. (For articles on Reichenbach see, e.g, Spohn 1991 and Salmon and Wolters 1994, Richardson 2005, 2006, and Milkov and Peckhaus 2013.) Moreover, here the emphasis must lie on the main protagonists: Schlick, Carnap and Neurath. (Neither Hahn or Frank, nor Waismann or Feigl, for instance, can be discussed here as extensively as their work deserves; see, e.g., Uebel 2005b, 2011b, McGuinness 2011, Haller 2003, respectively.) What will be noted, however, is that Vienna Circle philosophy was by no means identical with the post-World War II logical empiricism that has come to be known as the “received view” of scientific theories, even though it would be hard to imagine the latter without the former. (For a systematic if schematic critical discussion of the received view, see Suppe 1977, for a partial defense Mormann 2007a.)

To deepen the somewhat cursory overview of Vienna Circle philosophy given above, we now turn to the discussion of the following issues: first, the viability of the conceptions of empirical significance employed by Vienna Circle in its classical period; second, its uses of the analytic-synthetic distinction; third, its supposedly reductionist designs and foundationalist ambitions for philosophy; fourth, its stances in the debate about realism or anti-realism with regard to the theoretical terms in science; fifth, Carnap’s later ideas in response to some of the problems encountered; sixth, the issue of the status of the meaning criterion itself and of the point of their critique of metaphysics; seventh, the Vienna Circle’s attitude towards history and of their own place in the history of philosophy.

These topics have been chosen for the light their investigation throws on the Circle’s own agendas and the reception of its doctrines amongst philosophers at large, as well as for the relative ease with which their discussion allows its development and legacy to be charted. There can be little doubt about the enormous impact that the members of the Vienna Circle had on the development of twentieth-century philosophy. What is less clear is whether any of its distinctive doctrines are left standing once the dust of their discussion has settled or whether those of its teachings that were deemed defensible merged seamlessly into the broad church that analytic philosophy has become (and, if so, what those surviving doctrines and teachings may be).

It must be noted, then, that the topics chosen for this article do not exhaust the issues concerning which the members of the Vienna Circle made significant contributions (which continue to stimulate work in the history of philosophy of science). Important topics like that of the theory and practice of unified science, of the nature of the empirical basis of science (the so-called protocol-sentence debate) and of the general structure of the theories of individual sciences can only be touched upon selectively. Likewise, while the general topic of ethical non-cognitivism receives only passing mentions, the Circle’s varied approaches to value theory cannot be discussed here (for an overview see Rutte 1986). Other matters, like the contributions made by Vienna Circle members to the development of probability theory and inductive logic, the philosophy of logic and mathematics (apart from the guiding ideas of Carnap) and to the philosophy of individual empirical sciences (physics, biology, psychology, social science), cannot be discussed at all (see Creath and Friedman 2007 and Richardson and Uebel 2007 for relevant essays). But it may be noted that with his “logic of science” Carnap counts among the pioneers of what nowadays is called “formal epistemology”.

3.1 Verificationism and the Critique of Metaphysics

Not surprisingly, it was the Circle’s rejection of metaphysics by means of their seemingly devastating criterion of cognitive significance that attracted immediate opposition. (That they did not deny all meaning to statements thus ruled out of court was freely admitted from early on, but this “expressive” surplus was considered secondary to so-called “cognitive” meaning and discountable in science (see Carnap 1928b, 1932a).) Notwithstanding the metaphysicans’ thunder, however, the most telling criticisms of the criterion came from within the Circle or broadly sympathetic philosophers. When it was protested that failure to meet an empiricist criterion of significance did not make philosophical statements meaningless, members of the Circle simply asked for an account of what this non-empirical and presumably non-emotive meaning consisted in and typically received no convincing answer. The weakness of their position was rather that their own criterion of empirical significance seemed to resist an acceptable formal characterization.

To start with, it must be noted that long before the verification principle proper entered Circle’s discourse in the late 1920s, the thought expressed by Mach’s dictum that “where neither confirmation nor refutation is possible, science is not concerned” (1883 [1960, 587]) was accepted as a basic precept of critical reflection about science. Responsiveness to evidence for and against a claim was the hallmark of scientific discourse. (Particularly the group Frank-Hahn-Neurath, who formed part of a pre-World War I discussion group (Frank 1941, 1949a) sometimes called the “First Vienna Circle” (Haller 1985, Uebel 2003), can be presumed to be familiar with Mach’s criterion.) Beyond this, still in the 1920s, Schlick (1926) convicted metaphysics for falsely trying to express as logically structured cognition what is but the inexpressible qualitative content of experience. Already then, however, Carnap (1928b, §7) edged towards a formal criterion by requiring empirically significant statements to be such that experiential support for them or for their negation is at least conceivable. Meaningfulness meant the possession of “factual content” which could not, on pain of rendering many scientific hypotheses meaningless, be reduced to actual testability. Instead, the empirical significance of a statement had to be conceived of as possession of the potential to receive direct or indirect experiential support (via deductive or inductive reasoning).

In 1930, considerations of this sort appeared to receive a considerable boost due to Waisman’s reports of Wittgenstein’s meetings with him and Schlick. (Wittgenstein discussed the thesis “The meaning of its sentence is its verification” in conversations with Schlick and Waismann on 22 December 1929 and 2 January 1930 (see Waismann 1967 [1979]). The thesis was elaborated in Waismann’s “Theses” dated to “around 1930” which were presented as Wittgenstein’s considered views.) While Wittgenstein may have thought of this statement more as a constitutive principle of meaning, in the Circle it was put to work primarily as a demarcation criterion against metaphysics. Note that even though this early Wittgensteinian version of the meaning criterion required conclusive verifiability (which Carnap’s of 1928 did not), it also allowed for verifiability in principle only (and did not demand actual verifiability). Like Carnap’s notion of experiential support, this criterion worked with the mere conceivability of verifiability. (The demand for conclusive verifiability was discussed in the meetings with Wittgenstein.) By 1931, however, it had become clear to some that this would not do. What Carnap later called the “liberalization of empiricism” was underway and different camps became discernible within the Circle. It was over this issue that the so-called “left wing” with Carnap, Hahn, Frank and Neurath first distinguished itself from the “more conservative wing” around Schlick. (See Carnap 1936–37, 422 and 1963a, §9. Carnap 1936–37, 37n dated the opposition to strict verificationism to “about 1931”.)

In the first place, this liberalization meant the accommodation of universally quantified statements and the return, as it were, to salient aspects of Carnap’s 1928 conception. Everybody had noted that the Wittgensteinian verificationist criterion rendered universally quantified statements meaningless. Schlick (1931) thus followed Wittgenstein’s own suggestion to treat them instead as representing rules for the formation of verifiable singular statements. (His abandonment of conclusive verifiability is indicated only in Schlick 1936a.) By contrast, Hahn (1933, drawn from lectures in 1932) pointed out that hypotheses should be counted as properly meaningful as well and that the criterion be weakened to allow for less than conclusive verifiability. But other elements played into this liberalization as well. One that began to do so soon was the recognition of the problem of the irreducibility of disposition terms to observation terms (more on this presently). A third element was that disagreement arose as to whether the in-principle verifiability or support turned on what was merely logically possible or on what was nomologically possible, as a matter of physical law etc. A fourth element, finally, was that differences emerged as to whether the criterion of significance was to apply to all languages or whether it was to apply primarily to constructed, formal languages. Schlick retained the focus on logical possibility and natural languages throughout, but Carnap had firmly settled his focus on nomological possibility and constructed languages by the mid-thirties. Concerned with natural language, Schlick (1932, 1936a) deemed all statements meaningful for which it was logically possible to conceive of a procedure of verification; concerned with constructed languages only, Carnap (1936–37) deemed meaningful only statements for whom it was nomologically possible to conceive of a procedure of confirmation of disconfirmation.

Many of these issues were openly discussed at the Paris congress in 1935. Already in 1932 Carnap had sought to sharpen his previous criterion by stipulating that those statements were meaningful that were syntactically well-formed and whose non-logical terms were reducible to terms occurring in the basic observational evidence statements of science. While Carnap’s focus on the reduction of descriptive terms allows for the conclusive verification of some statements, it must be noted that his criterion also allowed universally quantified statements to be meaningful, provided they were syntactically and terminologically correct (1932a, §2). It was not until one of his Paris addresses, however, that Carnap officially declared the meaning criterion to be mere confirmability. Carnap’s new criterion required neither verification nor falsification but only partial testability so as now to include not only universal statements but also the disposition statements of science (see Carnap 1936–37; the English translation of the original Paris address (1936a [1949]) combines it with extraneous material). These disposition terms were thought to be linked to observation statements by a variety of reduction postulates or longer reduction chains, all of which provided only partial definitions (despite their name they provided no eliminative reductions). Though plausible initially, the device of introducing non-observational terms in this way gave rise to a number of difficulties which impugned the supposedly clear distinctions between logical and empirical matters and analytic and synthetic statements (Hempel 1951, 1963). Independently, Carnap himself (1939) soon gave up the hope that all theoretical terms of science could be related to an observational base by such reduction chains. This admission raised a serious problem for the formulation of a meaning criterion: how was one to rule out unwanted metaphysical claims while admitting as significant highly abstract scientific claims?

Consider that Carnap (1939, 1956b) admitted as legitimate theoretical terms that may be merely implicitly defined in calculi that are themselves only partially interpreted by correspondence rules between some select calculus terms and expressions belonging to an observational language (via non-eliminative reductions). The problem was that mere confirmability was simply too weak a meaning criterion to rule out some putative metaphysical claims. Moreover, this problem arose for both the statement-based approach to the criterion (taken by Carnap in 1928, by Wittgenstein in 1929/30, and by Ayer both in the first (1936) and the second editions (1946) of Language Truth and Logic) and for the term-based approach (taken by Carnap since 1932). For the former approach, the problem was that the empirical legitimacy of statements obtained via indirect testing also transferred to any expressions that could be truth-functionally conjoined to them (for instance, by the rule of ‘or’-introduction). Statements thus became empirically significant, however vacuous they had been on their own. For the term-based approach, the problem was that, given the non-eliminability of dispositional and theoretical terms, empirical significance was no longer ascribable to individual expressions in isolation but became a holistic affair, with little guarantee in turn for the empiricist legitimacy of all the terms now involved.

For most critics (even within the ranks of logical empiricism), the problem of ruling out metaphysical statements while retaining the terms of high theory remained unsolved. By 1950, in response to the troubles of Ayer’s two attempts to account for the indirect testing of theoretical statements via their consequences, Hempel conceded that it was “useless to continue to search for an adequate criterion of testability in terms of deductive relationships to observation sentences” (1950 [1959, 116]). The following year, Hempel also abandoned the idea of using, as a criterion of empirical significance, Carnap’s method of translatability into an antecedently determined empirical language consisting only of observational non-logical vocabulary. Precisely because it was suitably liberalized to allow abstract scientific theories with merely partial interpretations, its anti-metaphysical edge was blunted: it allowed for combination with “some set of metaphysical propositions, even if the latter have no empirical interpretation at all” (1951, 70). Hempel drew the holistic conclusion that the units of empirical significance were entire theories and that the measure of empirical significance itself was multi-criterial and, moreover, allowed for degrees of significance. To many, this amounted to the demise of the Circle’s anti-metaphysical campaign. By contrast, Feigl’s reaction (1956) was to reduce the ambition of the criterion of significance to the mere provision of necessary conditions.

Some further work was undertaken on rescuing and, again, debunking a version of the statement-based criterion, but not by (former) members of the Vienna Circle. However, in response to the problem of how to formulate a meaning criterion that suitably distinguished between empirically significant and insignificant non-observational terms, Carnap proposed a new solution in 1956 and another one in 1966. We will return to discuss these separately (see section 3.5 below); for now we need only note that these proposals were highly technical and applied only to axiomatized theories in formal languages. They too, however, found not much favor amongst philosophers. Yet whatever the problems that may or may not beset them, it would seem that far more general philosophical considerations contributed to the disappearance of the problem of meaning criterion from most philosophical discussions since the early 1960s (other than as an example of mistaken positivism). These include the increasing opposition to the distinctions between analytic and synthetic statements and observational and theoretical terms as well as a general sense of dissatisfaction with Carnap’s approach to philosophy which began to seem both too formalist in execution and too deflationary in ambition. The entire philosophical program of which the search for a precise criterion of empirical significance was a part had begun to fall out of favor (and with it technical discussions about the criterion’s latest version).

The widely perceived collapse of the classical Viennese project to find in an empiricist meaning criterion a demarcation criterion against metaphysics—we reserve judgement about Carnap’s last two proposals here—can be interpreted in a variety of ways. It strongly suggests that cognitive significance cannot be reduced to what is directly observable, whether that be interpreted in phenomenalist or intersubjective, physicalist terms. In that important but somewhat subsidiary sense, the collapse spelt the failure of many of the reductivist projects typically ascribed to Viennese neopositivism (but see section 3.3 below). Beyond that, what actually had failed was the attempt to characterize for natural languages the class of cognitively significant propositions by recursive definitions in purely logical terms, either by relations of deducibility or translatability. What failed, in other words, was the attempt to apply a general conception of philosophical analysis as purely formal, pursued also in other areas, to the problem of characterizing meaningfulness.

This general conception can be considered formalist in several senses. It was formalist, first, in demanding the analysis of the meaning of concepts and propositions in terms of logically necessary and sufficient conditions: it was precise and brooked no exceptions. And it was formalist, second, in demanding that such analyses be given solely in terms of the logical relations of these concepts and propositions to other concepts and propositions: it used the tools of formal logic. There is also a third sense that is, however, applicable predominantly to the philosophical project in Carnap’s hands, in that it was formalist since it concentrated on the analysis of contested concepts via their explication in formal languages. (Discussion of its viability must be deferred until sections 3.5 and 3.6 below, since what’s at issue currently is only the formalist project as applied to concepts in natural language.) The question arises whether all Vienna Circle philosophers concerned with empirical significance in natural language were equally affected, for the collapse of the formalist project may leave as yet untouched other ways of sustaining the objection that metaphysics is, in some relevant sense, cognitively insignificant. (Such philosophers in turn would have to answer the charge, of course, that only the formalist project of showing metaphysics strictly meaningless rendered the Viennese anti-metaphysics distinctive.)

Even though the formalist project became identified with mainstream logical empiricism generally (consider its prominence in confirmation theory and in the theory of explanation), it was not universally subscribed to in the Vienna Circle itself. In different ways, neither Schlick nor Neurath or Frank adhered to it. As noted in the overview above, Schlick’s attempts to exhibit natural language meaning abjured efforts to characterize it in explicitly formal terms, even though he accepted the demand for necessary and sufficient conditions of significance. In the end, moreover, Schlick turned away from his colleagues’ search for a criterion of empirical significance. In allowing talk of life after death as meaningful (1936a), for the very reason that what speaks against it is only the empirical impossibility of verifying such talk, Schlick’s final criterion clearly left empiricist strictures behind.

By contrast, Neurath and Frank kept their focus on empirical significance. While they rarely discussed these matters explicitly, their writings give the impression that Neurath and Frank chose to adopt (if not retain) a contextual, exemplar-based approach to characterizing the criterion of meaninglessness and so decided to forego the enumeration of necessary and sufficient conditions. Mach’s precept cited earlier is an example of such a pragmatic approach, as is, it should be noted, Peirce’s criterion of significance, endorsed by Quine (1969), which claims that significance consists in making a discernible difference whether a proposition is likely to be true or false. Mach’s pragmatic approach had been championed already before verificationism proper by Neurath, Frank and Hahn who became, like Carnap, early opponents of conclusive verifiability. (Indeed, it is doubtful whether Neurath’s radical fallibilism, most clearly expressed already in 1913, ever wavered.) This pragmatic understanding found clear expression in Neurath’s adoption (1935a, 1938) of K. Reach’s formulation of metaphysical statements as “isolated” ones, as statements that do not derive from and hold no consequences for those statements that we do accept on the basis of empirical evidence or for logical reasons. (Hempel’s dismissal, in 1951, of this pragmatic indicator presupposes the desiderata of the formalist project.) Finally, there is Frank’s suggestion (1963), coupled with his longstanding advice to combine logical empiricism with pragmatism, that Carnap’s purely logical critique of metaphysics in (1932a) was bound to remain ineffective as long as the actual use of metaphysics remained unexamined. It would be worth investigating whether—if the critique of the alleged reductionist ambitions of their philosophy could also be deflected (see section 3.3 below)—the impetus of the anti-verificationist critique can be absorbed by those with a pragmatic approach to the demarcation against metaphysics. Much as with Quine’s Peirce, such a criterion rules out as without interest for epistemic activity all concepts and propositions whose truth or falsity make no appreciable difference to the sets of concepts and propositions we do accept already.

An entirely different moral was drawn by Reichenbach (1938) and thinkers indebted to his probabilistic conception of meaning and his probabilistic version of verificationism, which escaped the criticisms surveyed above by vagaries of its own. Such theorists perceive the failure of the formalist model to accommodate the empirical significance of theoretical terms to stem from its so-called deductive chauvinism. In place of the exclusive reliance on the hypothetical-deductive method these theorists employ non-demonstrative analogical and causal inductive reasoning to ground theoretical statements empirically. Like Salmon, these theorists adopt a form of “non-linguistic empiricism” which they sharply differentiate from the empiricism of the Vienna Circle (Salmon 1985, 2003 and Parrini 1998).

Now against both the pragmatic and the post-linguistic responses to the perceived failure of the attempt to provide a precise formal criterion of significance serious worries can be raised. Thus it must be asked whether without a precise way of determining when a statement ‘makes an appreciable difference’, criticism of metaphysics based on such a criterion may be not be considered as a biased dismissal rather than a demonstration of fact and so fall short of what is needed. Likewise in the case of the anti-deductivist response, it must be noted that a criterion based on analogical reasoning will only be as effective as the strength of the analogy which can always be criticized as inapt (and similarly for appeals to causal reasoning). The very point of exact philosophy in a scientific spirit—for many the very point of Vienna Circle philosophy itself—seems threatened by such maneuvres. Acquiescence in the perceived failure of the proposed criteria of significance thus comes with a price: if not that of abandoning Vienna Circle philosophy altogether, then at least that of formulating an alternative understanding to how some of its ambitions ought to be understood. (Recent reconstructive work on Carnap, Neurath and Frank may be regarded in this light.)

A still different response—but one emblematic for the philosophical public at large—is that of another of Reichenbach’s former students, Putnam, who has come to reject the anti-metaphysical project that powered verificationism in its entirety. Repeatedly in his later years, Putnam has called for a refashioning of analytic philosophy as such, providing, as it were, a philosophically conservative counterweight to Rorty’s turn to postmodernism. Putnam’s reasons (the alleged self-refutation of the meaning criterion) are still different from those surveyed above and will be discussed when we return to reconsider the very point of the Circle’s campaign against metaphysics (see section 3.6 below).

3.2 The Analytic/Synthetic Distinction and the Relative A Priori

Whether the verificationist agenda was pursued in a formalist or pragmatic vein, however, all members shared the belief that meaningful statements divided exclusively into analytic and synthetic statements which, when asserted, were strictly matched with a priori and a posteriori reasoning for their support. The Vienna Circle wielded this pairing of epistemic and semantic notions as a weapon not only against the substantive a priori of the Schoolmen but also against Kant’s synthetic a priori. Moreover, their notion of analyticity comprized both logical and mathematical truths, thereby extending Wittgenstein’s understanding of the former as “tautological” in support of a broadly logicist program.

It is well known that this central component of the Vienna Circle’s arsenal, the analytic/synthetic distinction, came under sharp criticism from Quine in his “Two Dogmas of Empiricism” (1951a), less so that the criticism can only be sustained by relying on objections of a type first published by Tarski. The argument is more complex, but here is a very rough sketch. So as to discard the analytic/synthetic distinction as an unwarranted dogma, Quine in “Two Dogmas” argued for the in-principle revisability of all knowledge claims and criticised the impossibility of defining analyticity in a non-circular fashion. The first argument tells against the apodictic a priori of old (the eternal conceptual verities), but, as we shall see, it is unclear whether it tells against at least some of the notions of the a priori held in the Vienna Circle. The second argument presupposes a commitment to extensionalism that likewise can be argued not to have been shared by all in the Circle. By contrast, Tarski had merely observed that, at a still more fundamental level, he knew of no basis for a sharp distinction between logical and non-logical terms. (For relevant primary source materials see also Quine 1935, 1951b, 1963, Carnap 1950, 1955, 1963b, their correspondence and related previously unpublished lectures and writings in Creath 1990, the memoir Quine 1991, and Tarski 1936.)

The central role on the Vienna Circle’s side in this discussion falls to Carnap and the reorientation of philosophy he sought to effect in Logical Syntax (1934/37). It was the notion of the merely relative and therefore non-apodictic a priori that deeply conditioned his notion of analyticity and allowed him to sidestep Quine’s fallibilist argument in a most instructive fashion. In doing so Carnap built on an idea behind Reichenbach’s early attempt (1920) to comprehend the general theory of relativity by means of the notion of a merely constitutive a priori. Now Schlick had objected to the residual idealism of this proposal (see Oberdan 2009) and prefered talk of conventions instead and Reichenbach soon followed him in this (see Coffa 1991, Ch. 10). Carnap too did not speak of the relative a priori as such (in returning to this terminology present discussions follow Friedman 1994), but his pluralism of logico-linguistic frameworks furnish precisely that.

First consider Schlick as a contrast class. Schlick (1934) appeared to show little awareness of the language-relativity of the analytic/synthetic distinction and spoke of analytic truths as conceptual necessities that can be conclusively surveyed. This would suggest that Schlick rejected Kant’s apodictic synthetic a priori but not the apodicity of analytic statements. Clearly, if that were so, Quine’s argument from universal fallibilism would find a target here. Matters are not quite so clear-cut, however. Schlick had long accepted the doctrine of semantic conventionalism that the same facts could be captured by different conceptual systems (1915): his analytic truths were conventions that were framework-relative and as such necessary only in the very frameworks they helped to constitute. Yet what Schlick did not countenance was the possibility of incommensurable conceptual frameworks. He held that any fact was potentially expressible in any framework (1936b). As a result, Schlick did not accept the possibility that after the adoption of a new framework the analytic truths of the old one may be no longer assertable, that they could be discarded as no longer applicable even in translation, as it were. Herein lay a point that Quine’s argument could exploit: Schlick’s analytic truths remained unassailable despite their language-relativity.

Now Carnap, under the banner of the principle of logical tolerance (1934/37, §17), abandoned the idea of the one universal logic which had informed Frege, Russell and Wittgenstein before him. Instead, he recognized a plurality of logics and languages whose consistency was an objective matter even though axioms and logical rules were fixed entirely by convention. Already due to this logical pluralism, the framework-relativity of analytic statements went deeper for Carnap than it did for Schlick. But Carnap also accepted the possibility of incommensurability between seemingly similar descriptive terms and between entire conceptual systems (1936a). Accepting the analytic truths of the framework of our best physical theory may thus be incompatible with accepting those of an earlier one, even if the same logic is employed in both. Carnapian analyticities do not therefore express propositions that we hold to be true unconditionally, but only propositions true relative to their own framework. Carnapian analyticities are no longer held to be potentially translatable across all frameworks. Quine’s claim of universal revisability (which itself needs some modification; see Putnam 1978) thus misses its mark against them. (Quine, of course, rejected Carnap’s intensionalist accommodation of radical fallibilism via the notion of language change.)

Concerning the criticism of the circular nature of the definition of analyticity, Carnap responded that it pertained primarily to the idea of analyticity in natural language whereas he was interested in “explications” as provided by the logic of science (or better, a logic of science, since there existed no unique logic of science for Carnap). Explications are reconstructions in a formal language of selected aspects of complex terms that should not be expected to model the original in all respects (1950b, Ch.1). Moreover, Carnap held that explication of the notion of analyticity in formal languages yielded the kind of precision that rendered the complaint of circularity irrelevant: vague intuitions of meaning were no longer relied upon. Those propositions of a given language were analytic that followed from its axioms and, once the syntactic limitations of the Logical Syntax period had been left behind, from its definitions and meaning postulates, by application of its rules: no ambiguity obtained.

So it may appear that the notion of analyticity is easily delimitable in Carnap’s explicational approach: analytic propositions would be those that constitute a logico-linguistic framework. But complications arose from the fact that, on Carnap’s understanding, not all propositions defining a logico-linguistic framework need be analytic ones (1934/37, §51). It was possible for a framework to consist not only of L-rules, whose entirety determines the notion of logical consequence, but also of P-rules, which represent presumed physical laws. So let analytic propositions be those framework propositions whose negations are self-contradictory. Here a problem arose once the syntactic constraints were dropped by Carnap after Logical Syntax so as to allow semantic reasoning and the introduction of so-called meaning postulates: now the class of analytic propositions was widened to include not only logical and mathematical truths but also those obtained by substitution of semantically equivalent expressions. How was one now to explicate the idea that there can be non-analytic framework propositions (whose negations are not self-contradictory)? Consider that for opponents like Quine, responding that the negations of non-analytic framework propositions do not contradict meaning postulates, was merely to dress up a presupposed notion of meaning in pseudo-formal garb: while it provided what looked like formal criteria, Carnap’s method did not leave the circle of intensional notions behind and so seemed to beg the question. Meaning postulates (Carnap 1952), after all, could only be identified by appearing on a list headed “meaning postulates” (as Quine added in reprints of 1951a).

Here one must note that in Logical Syntax, Carnap also modified the thesis of extensionality he had previously defended alongside Russell and Wittgenstein: now it merely claimed the possibility of purely extensional languages and no longer demanded that intensional languages be reduced to them (ibid., §67). Of course, the mere claim that the language of science can be extensional still proves troublesome enough, given that in such a language a distinction between laws and accidentally true universal propositions cannot be drawn (the notion of a counterfactual conditional, needed to distinguish the former, is an intensional one). Even so, this opening of Carnap’s towards intensionalism already at the height of his syntacticism—to say nothing of his explicit intensionalism in Meaning and Necessity (1947)—seems enough to thwart Quine’s second complaint in “Two Dogmas”. Carnap did not share Quine’s extensionalist agenda, so the need to break out of the circle of intensional notions once these were clearly defined in his formal languages did not apply. That their’s were in fact different empiricist research programmes was insufficiently stressed, it would appear, by Quine and Quinean critics of Carnap (Stein 1992; cf. Ricketts 1982, 2003, Creath 1991, 2004, Richardson 1997).

To sustain his critique, Quine had to revive his and Tarski’s early doubts about Carnap’s methodological apparatus and dig even deeper. (Tarski also shared Quine’s misgivings about analyticity when they discussed these issues with Carnap at Harvard; see Mancosu 2005, Frost-Arnold 2013.) Their scepticism found its target in Carnap’s ingenious measures in Logical Syntax taken to preserve the thesis that mathematics is analytic from the ravages of Gödel’s incompleteness theorems. Gödel proved that every formal system strong enough to represent number theory contains a formula that is true but neither itself or its negation is provable in that system; such formulae—known since as Gödel sentences—are provable in a still stronger system which, however, also contains a formula of its own that is true but not provable in it (and neither is its negation). Commonly, Gödel’s proof is taken to have undermined the thesis of the analyticity of arithmetic. (For discussions of this challenge to Carnap’s logical syntax project, see Friedman 1988, 1999a, Goldfarb and Ricketts 1992, Richardson 1994, Awodey and Carus 2003, 2004.) Carnap responded by stating that arithmetic demands an infinite sequence of ever richer languages and by declaring analytic statements to be provable by non-finite reasoning (1934/37, §60a-d). This looked like fitting the bill on purely technical grounds, but it is questionable whether such reasoning may still count as syntactic. Nowadays, it is computational effectiveness that is taken to distinguish purely formal from non-formal, material reasoning. (Carnap’s move highlights the tension within Logical Syntax between formal and crypto-semantic reasoning. It thus points ahead to his acceptance of semantics in 1935—only one year after the publication of Logical Syntax and contrary to his opposition against it expressed in that book—that the rigid syntacticism officially advertised there was at the same time undermined as its failings were being compensated (illegitimately so by official standards), e.g., by considering translatability a syntactic notion. For a discussion of Carnap’s move, see Coffa 1978, Ricketts 1996, Goldfarb 1997, Creath 1996, 1999.) It is no criticism that Carnap’s reconstruction of arithmetic was not standard logicism, but that Carnap unduly stretched the idea of formal reasoning is. Was he saved by his shift to semantics?

Tarski (1936) granted the language-relativity of the reconstructed notion of analyticity in Logical Syntax. He also did not object that Carnap’s procedure of circumventing the problem which the Gödel sentences presented to the thesis of the analyticity of arithmetic was illegitimate. Tarski rather questioned whether there were “objective reasons” for the sharp distinction between logical and non-logical terms and he pointed out that Carnap’s distinction between the logical and the empirical was not a hard and fast one. Since noting that the distinction between logical and non-logical was not a sharp one and arguing that no principled distinction could be upheld between them are two quite different reactions, however, Tarski’s point on its own does not fully support the Quinean critique. Quine’s conclusion (1940, §60) that the notion of logical truth itself is “informal” rather reflects the moral that he drew from Tarski’s observation. It appears that what motivated him (after a nominalistic interlude) to develop his naturalistic alternative to Carnap’s conception of philosophy was his considered rejection of Carnap’s accommodation of the thesis that arithmetic is analytic to Gödel’s result.

Different strands of Quine’s criticism of the analytic/synthetic distinction must thus be distinguished. While Quine’s criticisms in “Two Dogmas” on their own clearly did not undermine all forms of the distinction that were defended in the Vienna Circle—Carnap’s reconstructions of the notion of analyticity did not express unconditionally necessary and unrevisable propositions—they do gain in plausibility even against Carnap’s once it is recognized that the deepest ground of contestation lies elsewhere: not in the notion of analyticity widely understood but in that of logical truth narrowly understood. Read in this way, Quine can be seen to argue that the notion of L-consequence as explication of analytic truth—as opposed to P-consequence as non-analytic, mere framework entailments—traded not only on the idea of non-finitary notions of proof but also on a distinction of logical from descriptive expressions that itself only proceeded on the basis of a finite enumeration of the former (compare Carnap 1934/37, §§51–52). (This deficit was not repaired in Carnap’s later work either; see Awodey 2007.) What Quine criticized was precisely the fact that Carnap could ground the distinction between logical and non-logical terms no deeper than by the enumeration of the former in a given framework: was the distinction therefore not quite arbitrary?

Quine’s direct arguments against the distinction between logical and empirical truth (1963) have been found to beg the question against Carnap and his way of conceiving of philosophy (Creath 2003). This way of responding to Quine’s objection requires us to specify still more precisely just what Carnap thought he was doing when he employed the distinction between analytic and synthetic propositions. To be sure, in (1955) he gave broadly behavioural criteria for when meaning ascriptions could be deemed accepted in linguistic practice, but in (1963a) he noted that this was not a general requirement for the acceptability of explicatory discourse. To repeat, explications did not seek to model natural language concepts in their tension-filled vividness, but to make proposals for future use and to extract and systematize certain aspects for constructive purposes. Thus Carnap clarified (1963b, §32) that he regarded the distinction between analytic and synthetic statements—just like the distinction between descriptive or factual and prescriptive or evaluative statements—not as descriptive of natural language practices, but as a constructive tool for logico-linguistic analysis and theory construction. It is difficult to overstress the significance of this stance of Carnap’s for the evaluation of his version of the philosophical project of the Vienna Circle. Carnap’s understanding of philosophy has thus been aptly described as the “science of possibilities” (Mormann 2000).

As Carnap understood the analytic/synthetic distinction, it was a distinction drawn by a logician to enable greater theoretical systematicity in the reconstructive understanding of a given symbol system, typically a fragment of a historically developed one. That fully determinative objective criteria of what to regard as a logical and what as a non-logical term cannot be assumed to be pre-given does not then in and of itself invalidate the use of that distinction by Carnap. On the contrary, it has been convincingly argued that Carnap himself did not hold to a notion of what is a factual and what is a formal expression or statement that was independent of the specification of the language in question (Ricketts 1994). The ultimate ungroundedness of his basic semantic explicatory categories, this suggests instead, was a fact that his own theories fully recognized and consciously exploited. (Somewhat analogously, that we cannot define science independently of the practice of scientists of “our culture” was admitted by Neurath 1932a, Carnap 1932d and Hempel 1935, much to exasperation of Zilsel 1932 and Schlick 1935a.)

It remained open for Carnap then to declare his notion of analyticity to be only operationally defined for constructed languages and to let that notion be judged entirely in terms of its utility for meta-theoretical reflection. Just on that account, however, a last hurdle remains: finding a suitable criterion of significance for theoretical terms that allows the distinction between analytic and synthetic statements to be drawn in the non-observational, theoretical languages of science. (This was a problem ever since the non-eliminative reducibility of disposition terms had been accepted and one that still held for Carnap’s 1956 criterion; see section 3.5 below). Only if that can be done, we must therefore add, can Carnap claim his formalist explicationist project to emerge unscathed from the criticisms of both Tarski and Quine.

An important related though independently pursued line of criticism may be noted here. It finds its origin in Saunders Mac Lane’s review (1937) of Carnap’s Logical Syntax and focusses less on the analytic/synthetic distinction than on Carnap’s failure to give a formally correct definition of logic. It challenges the ambition to have accounted for the formal sciences but declines to embrace a naturalistic alternative. Further research along these lines has suggested to some that by extending Carnap’s approach and framework it can be linked to attempts in category theory to provide the missing definition (see Awodey 2012, 2016).

None of the above considerations should lead one to deny, however, that one can find understandings of the term “analytic” by members of the Vienna Circle (like Schlick) that do fall victim to the criticisms of Quine more easily. Nor should one discount the fact that Carnap’s logic of science emerges as wilfully ill-equipped to deal with the problems that exercise the traditional metaphysics or epistemologies that deal in analyticities. (Of course, unlike his detractors, Carnap considered this to be a merit of his approach.) Lastly, it must be noted that Carnap’s intensionalist logic of science holds out the promise of practical utility only for the price of a pragmatic story that remains to be told. Of what nature are the practical considerations and decisions that, as Carnap so freely conceded (1950a), are called for when choosing logico-linguistic frameworks? (Such conventional choices do not respond to truth or falsity, but instead to whatever is taken to measure convenience.) That Carnap rightly may have considered such pragmatic questions beyond his own specific brief as a logician of science does not obviate the need for an answer to the question itself. (Carus 2007 argues that in this broad pragmatic dimension lies the very point of Carnap’s explicationism.) On this issue, too, it would have been helpful if there had been more collaboration with Neurath and Frank, who were sympathetic to Carnap’s explication of analyticity but did not refer to it much in their own, more practice-oriented investigations (see section 3.6 below).

3.3 Reductionism and Foundationalism: Two Criticisms Partly Rebutted

As it happens, anti-verificationism has two aspects: opposition to meaning reductionism and opposition to the formalist project. Turning to the former, we must distinguish two forms of reductionism, phenomenalist and physicalist reductionism. Phenomenalism holds statements to be cognitively significant if they can be reduced to statements about one’s experience, be it outer (senses) or inner (introspection). Physicalism holds statements to be cognitively significant if they can be reduced or evidentially related to statements about physical states of affairs. Here it must be noted not only that the Vienna Circle is typically remembered in terms of the apparently phenomenalist ambitions of Carnap’s Aufbau of 1928, but also that already by the early 1930s some form of physicalism was favoured by some leading members including Carnap (1932b) and that already in the Aufbau the possibility of a different basis than the phenomenal one had been indicated. Thus one must not only ask about the reductionism in the Aufbau but also consider just how reductivist in intent the physicalism was meant to be.

Considerations can begin with an early critique that has given rise in some quarters to a sharp distinction between Viennese logical positivism and German logical empiricism, with the former accused of reductionism and the latter praised for their anti-reductionism, a distinction which falsely discounts the changing nature and variety of Vienna Circle doctrines. Reichenbach’s defense of empiricism (1938) turned on the replacement of the criterion of strict verifiability with one demanding only that the degree of probability of meaningful statements be determinable. This involved opposition also to demands for the eliminative reduction of non-observational to observational statements: both phenomenalism and reductive physicalism were viewed as untenable and a correspondentist realism was advanced in their stead. Now it is true that of the members of the Vienna Circle only Feigl ever showed sympathies for scientific realism, but it is incorrect that all opposition to it in the Circle depended on the naive semantics of early verificationism. Again, of course, some Vienna Circle positions were liable to Reichenbach’s criticism.

Another misunderstanding to guard against is that the Vienna Circle’s ongoing concern with “foundational issues” and the “foundations of science” does in itself betoken foundationalism. (In the Vienna Circle’s days, foundationalism had it that the basic items of knowledge upon which all others depended were independent of each other, concerned phenomenal states of affairs and were infallible; nowadays, foundationalists drop phenomenalism and infallibility.) Already the manifesto sought to make clear the Circle’s opposition when it claimed that “the work of ‘philosophic’ or ‘foundational’ investigations remains important in accord with the scientific world conception. For the logical clarification of scientific concepts, statements and methods liberates one from inhibiting prejudices. Logical and epistemological analysis does not wish to set barriers to scientific enquiry; on the contrary, analysis provides science with as complete a range of formal possibilities as is possible, from which to select what best fits each empirical finding (example: non-Euclidean geometries and the theory of relativity).” (Carnap-Hahn-Neurath 1929 [1973, 316]) This passage can be read as an early articulation of the project of a critical-constructivist meta-theory of science that abjures a special authority of its own beyond that stemming from the application of the methods of the empirical and formal sciences to science itself, but instead remains open to what the actual practice of these sciences demands.

How then can Vienna Circle philosophy be absolved of reductionism? As noted, it is the Aufbau (and echoes of it in the manifesto) that invites the charge of phenomenalist reductionism. To begin with, one must distinguish between the strategy of reductionism and the ambition of foundationalism. Concerning the Aufbau it has been argued that its strategy of reconstructing empirical knowledge from the position of methodological solipsism (phenomenalism without its ontological commitments and some of its epistemological ambitions) is owed not to foundationalist aims but to the ease by which this position seemed to allow the demonstration of the interlocking and structural nature of our system of empirical concepts, a system that exhibited unity and afforded objectivity, which was Carnap’s main concern. (See Friedman 1987, 1992, Richardson 1990, 1998, Ryckman 1991, Pincock 2002, 2005. For the wide variety of influences on the Aufbau more generally, see Damböck 2016.) However, it is hard to deny categorically that Carnap ever harbored foundationalist ambitions. Not only did Carnap locate his Aufbau very close to foundationalism in retrospect (1963a), but a passage in his (1930) led Uebel (2007) to claim that around 1929/30 Carnap was motivated by foundationalist principles and reinterpreted his own Aufbau along these lines—around the same time that Wittgenstein entertained a psychologistic reinterpretation of his own Tractatus that was reported back to the Circle by Waismann. To correct this foundationalist aberration was the task of the Circle’s subsequent protocol-sentence debate about the content, form and status of the evidence statements of science.

This concession to the foundationalist misinterpretation of Vienna Circle philosophies generally must not, however, be taken to tell against the new reading of the Aufbau or the epistemologies developed from 1930 onwards on the physicalist wing of the Circle, however. In fact, the Aufbau itself fails when it is read as a foundationalist project, as it was by Quine (1951a) who pointed out that no eliminative definition of the relation ‘is at’ was provided (required for locating objects of consciousness in physical space). To be sure, this did not prompt Carnap (1961a) to abandon as mistaken reconstructions of the scientific language on the basis of methodological solipsism. Likewise, Carnap had not been prompted do so some thirty years earlier by Neurath (1931b, 1932a) who argued that such a type of rational reconstruction traded on objectionable counterfactual presuppositions (methodological solipsism did not provide a correct description of the reasoning involved in cognitive commerce with the world around us). All along Carnap (1932e, 1961a) merely conceded that it was more “convenient” to reconstruct the language of science on a physicalistic basis. Carnap’s responses are best interpreted, however, not as clinging to lost epistemological foundations, but as indicating a logician’s overriding concern with explicative language constructions of great variety and his long-standing and radical ontological abstemiousness. (Except for the period singled out above, the case for foundationalism is not supported either by the fact that as a logician of science Carnap gave up on what he now considered an epistemology unduly “entangled with psychological questions” (1934/37, §72). Already his concern in the Aufbau with different constructional systems speaks against it; moreover, philosophical scepticism never worried him.)

Concerning physicalism likewise it may thus be asked whether it was only the recognition of the irreducibility of disposition terms, let alone of purely theoretical terms, that spelt the end of any earlier foundationalist impulse. Already by (1932e), however, Carnap’s physicalism was explicitly anti-foundationalist. That later in (1936/37) he called his non-eliminative definitions of disposition terms “reduction sentences” indicates that it was enough for him to provide a basis for the applicability of these terms by merely sufficient but not necessary conditions. Likewise, Carnap’s proposal (1939) to conceive of theoretical terms as defined by implicit definition in a non-interpreted language, but linked as a system via correspondence rules to terms for which a reductive chain can be determined, suggest that what concerned him primarily was the capture of indicator relations to sustain in principle testability of statements containing the terms in question. This is best understood as an attempt to preserve the empirical applicability of the formal languages constructed by way of explication for the contested concepts of scientific methodology, but not as reductivism with regard to some foundational given.

By partial contrast, Neurath’s own physicalism all along was fallibilist and anti-foundationalist (1931b, 1932a). Consider that his complex conception of the form of protocol statements (1932b) explicated the concept of observational evidence in terms that expressly reflected debts to empirical assumptions which called for theoretical elaboration in turn. For unlike the logician of science Carnap, who left it to psychology and brain science to determine more precisely what the class observational predicates were that could feature in protocol statements (1936/37), the empirically oriented meta-theoretician of science Neurath was concerned to encompass and comprehend the practical complexities of reliance on scientific testimony: the different clauses (embeddings) of his proposed protocol statements stand for conditions on the acceptance of such testimony (see Uebel 2009). In addition, Neurath’s theory of protocol statements also makes clear that his understanding of physicalism did not entail the eliminative reduction of the phenomenon of intentionality but, like Carnap (1932c), merely sought its integration into empiricist discourse.

Given these different emphases of their respective physicalisms, mention must also be made of the significant differences between Carnap’s and Neurath’s conceptions of unified science: where the formalist Carnap once preferred a hierarchical ordering of finitely axiomatized theoretical languages that allowed at least partial cross-language definitions and derivations—these requirements were liberalized over the years (1936b), (1938), (1939)—the pragmatist Neurath opted from the start to demand only the interconnectability of predictions made in the different individual sciences (1935a), (1936c), (1944). (Metereology, botany and sociology must be combinable to predict the consequences of a forest fire, say, even though each may have its own autonomous theoretical vocabulary.) Here too it must be remembered that, unlike Carnap, Neurath only rarely addressed issues in the formal logic of science but mainly concerned himself with the partly contextually fixed pragmatics of science. (One exception is his 1935b, a coda to his previous contributions to the socialist calculation debate with Ludwig von Mises and others.) Not surprisingly, at times the priorities set by Neurath for the pragmatics of science seemed to conflict with those of Carnap’s logic of science. (These tensions often were palpable in the grand publication project undertaken by Carnap and Neurath in conjunction with Morris, the International Encyclopedia of the Unity of Science (Reisch 2003).) That said, however, note that Carnap’s more hierarchical approach to the unity of science also does not support the attribution of foundationalist ambitions.

But for a brief lapse around 1929/30, then, the post-Aufbau Carnap fully represents the position of Vienna Circle anti-foundationalism. In this he joined Neurath whose long-standing anti-foundationalism is evident from his famous simile, first used in 1913, that likens scientists to sailors who have to repair their boat without ever being able to pull into dry dock (1932b). Their positions contrasted at least prima facie with that of Schlick (1934) who explicitly defended the idea of foundations in the Circle’s protocol-sentence debate. Even Schlick conceded, however, that all scientific statements were fallible ones, so his position on foundationalism was by no means the traditional one. The point of his “foundations” remained less than wholly clear and different interpretation of it have been put forward. (On the protocol sentence debate as a whole, which included not only the debate between Carnap and Neurath but also that between the physicalists and Schlick, see, e.g., the differently centered accounts of Uebel 1992, 2007, Oberdan 1993, Cirera 1994.) While all in the Circle thus recognized as futile the attempt to restore certainty to scientific knowledge claims, not all members embraced positions that rejected foundationalism tout court

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