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Verificationism, also known as the verification principle or the verifiability criterion of meaning, is the philosophical doctrine which asserts that a statement is meaningful only if it is either empirically verifiable (i.e. confirmed through the senses) or a truth of logic (e.g., tautologies).

Verificationism rejects statements of metaphysics, theology, ethics, and aesthetics, as cognitively meaningless.[1][2] Such statements may be meaningful in influencing emotions or behavior, but not in terms of conveying truth value, information, or factual content.[3] Verificationism was a central theme of logical positivism, a movement in analytic philosophy that emerged in the 1920s by philosophers who sought to unify philosophy and science under a common naturalistic theory of knowledge.


Although earlier philosophical principles which aim to ground scientific theory in some verifiable experience are found within the work of American pragmatist C.S. Peirce and that of French conventionalist Pierre Duhem,[4] who fostered instrumentalism,[5] the project of verificationism was launched by the logical positivists who, emerging from the Berlin Circle and the Vienna Circle in the 1920s, sought an epistemology whereby philosophical discourse would be, in their perception, as authoritative and meaningful as an empirical science.

Logical positivists garnered the verifiability criterion of cognitive meaningfulness from Ludwig Wittgenstein's philosophy of language posed in his 1921 book Tractatus,[6] and, led by Bertrand Russell, sought to reformulate the analytic–synthetic distinction in a way that would reduce mathematics and logic to semantical conventions. This would be pivotal to verificationism, in that logic and mathematics would otherwise be classified as synthetic a priori knowledge and defined as "meaningless" under verificationism.

Seeking grounding in such empiricism as of David Hume,[7] Auguste Comte, and Ernst Mach—along with the positivism of the latter two—they borrowed some perspectives from Immanuel Kant, and found the exemplar of science to be Albert Einstein's general theory of relativity.


Logical positivists within the Vienna Circle recognized quickly that the verifiability criterion was too stringent. Notably, universal generalizations are empirically unverifiable, such that, under verificationism, vast domains of science and reason, such as scientific hypothesis, would be rendered meaningless.[8]

Rudolf Carnap, Otto Neurath, Hans Hahn and Philipp Frank led a faction seeking to make the verifiability criterion more inclusive, beginning a movement they referred to as the "liberalization of empiricism". Moritz Schlick and Friedrich Waismann led a "conservative wing" that maintained a strict verificationism. Whereas Schlick sought to reduce universal generalizations to frameworks of 'rules' from which verifiable statements can be derived,[9] Hahn argued that the verifiability criterion should accommodate to less-than-conclusive verifiability.[10] Among other ideas espoused by the liberalization movement were physicalism, over Mach's phenomenalism, coherentism over foundationalism, as well as pragmatism and fallibilism.[8][11]

In 1936, Carnap sought a switch from verification to confirmation.[8] Carnap's confirmability criterion (confirmationism) would not require conclusive verification (thus accommodating for universal generalizations) but allow for partial testability to establish "degrees of confirmation" on a probabilistic basis. Carnap never succeeded in formalizing his thesis despite employing abundant logical and mathematical tools for this purpose. In all of Carnap's formulations, a universal law's degree of confirmation is zero.[12]

That same year saw the publication of A. J. Ayer's work, Language, Truth and Logic, in which he proposed two types of verification: strong and weak. This system espoused conclusive verification, yet accommodated for probabilistic inclusion where verifiability is inconclusive. Ayer also distinguished between practical and theoretical verifiability. Under the latter, propositions that cannot be verified in practice would still be meaningful if they can be verified in principle.[13][14]


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Verificationism has been criticized by some philosophers, such as Karl Popper, another graduate of the University of Vienna though not part of the Vienna Circle. Popper gave three corn criticisms of verificationism:[15]

  1. Verificationism rejects universal generalizations, like "all swans are white," as meaningless. Popper argues that while universal statements cannot be verified, they can be proven false. Further, Popper argues that universals can be scientifically useful.
  2. Verificationism allows for some obviously false existential statements, such as "werewolves exist," to be classified as scientifically meaningful because one could possibly find one somewhere that they have not yet looked.
  3. By its own logic, the verificationism is meaningless because it cannot be empirically verified.

In The Logic of Scientific Discovery (1959), Popper proposed falsifiability as a preferable method for determining if a hypothesis is scientific, though it has been misunderstood as a revision of verificationism.[6][16] Informed by the contrasting approaches of Albert Einstein and Sigmund Freud, Popper proposed falsifiability as a standard specific to the sciences, rather than as a theory of meaning.[6] Popper noticed that Einstein sought out data that would disprove his theories; he made predictions about future instances based upon the past, and then tried to learn more to test the validity of his hypothesis. Freud, on the other hand, used data that could be shaped to fit his theories, and his theories were crafted to explain the past, not the future. For Popper, this clarified a key difference between science and pseudoscience.[17][18]

Popper regarded scientific hypotheses to be never completely verifiable, as well as not "confirmable" under Rudolf Carnap's thesis.[6][19] It is pseudoscientists that come to a conclusion and seek out information to verify their claim. Scientists, on the other hand, use a hypothesis to indicate the most likely possible explanation based on current data, and they seek to prove the hypothesis wrong so that they can continue to learn.[17] Popper also found that some non-scientific, metaphysical, ethical and aesthetic statements were, indeed, rich in meaning and important in the origination of scientific theories.[6]

Other philosophers have voiced their own criticisms of verificationism:


Malachi Haim Hacohen, in his biography of Popper, said that logical positivists practiced Popper's principles—conjecturing and refuting—until they ran their course, catapulting Popper, initially a contentious misfit, to carry the richest philosophy out of interwar Vienna.[16] Popper's critical rationalism posed its own criterion, falsifiability, to ensure that empiricism anchors scientific theory.[4]

In a 1979 TV interview, A. J. Ayer, who had introduced logical positivism to the English-speaking world in the 1930s,[25] was asked what he saw as its main defects, and answered that "nearly all of it was false".[24] However, he soon said that he still held "the same general approach".[24] The "general approach" of empiricism and reductionism—whereby mental phenomena resolve to the material or physical, and philosophical questions largely resolve to ones of language and meaning—has run through Western philosophy since the 17th century and lived beyond logical positivism's fall.[24]

In 1977, Ayer recognized that the verification principle was not widely accepted but acknowledged that it still held relevance and was being utilised. "The attitude of many philosophers reminds me of the relationship between Pip and Magwitch in Dickens's Great Expectations. They have lived on the money, but are ashamed to acknowledge its source".[4] In the late 20th and early 21st centuries, the general concept of verification criteria—in forms that differed from those of the logical positivists—was defended by Bas van Fraassen, Michael Dummett, Crispin Wright, Christopher Peacocke, David Wiggins, Richard Rorty, and others.[4]

See also


  1. ^ "verification principle". Oxford Reference. Retrieved 2023-07-09.
  2. ^ "Logical Positivism Revisited" (PDF).
  3. ^ Editors of Encyclopædia Britannica, "Verifiability principle", Encyclopædia Britannica, Website accessed 12 Mar 2014.
  4. ^ a b c d e C. J. Misak, Verificationism: Its History and Prospects (New York: Routledge, 1995), p. viii.
  5. ^ Miran Epstein, ch 2 "Introduction to philosophy of science", in Clive Seale, ed, Researching Society and Culture, 3rd edn (London: Sage Publications, 2012), pp. 18–19.
  6. ^ a b c d e Karl Popper, ch 4, subch "Science: Conjectures and refutations", in Andrew Bailey, ed, First Philosophy: Fundamental Problems and Readings in Philosophy, 2nd edn (Peterborough Ontario: Broadview Press, 2011), pp. 338–42.
  7. ^ Despite Hume's radical empiricism, set forth near 1740, Hume was also committed to common sense, and apparently did not take his own skepticism, such as the problem of induction, as drastically as others later did [Antony G Flew, A Dictionary of Philosophy, rev 2nd edn (New York: St Martin's Press, 1984), "Hume", p. 156].
  8. ^ a b c Sahotra Sarkar and Jessica Pfeifer, eds, The Philosophy of Science: An Encyclopedia, Volume 1: A–M (New York: Routledge, 2006), "Rudolf Carnap", p. 83.
  9. ^ Moritz Schlick, 1931, "Die Kausalität in der gegenwärtigen Physik", Die Naturwissen-schaften, 19: 145–162; transl. "Causality in Contemporary Physics" in Schlick 1979b, pp. 176–209
  10. ^ Hahn, Hans, 1933, Logik, Mathematik und Naturerkennen, Wien: Gerold, transl. "Logic, Mathematics, and Knowledge of Nature", in B. McGuiness 1987, pp. 24–45.
  11. ^ Antony G Flew, A Dictionary of Philosophy, rev 2nd edn (New York: St Martin's Press, 1984), "Neurath", p. 245.
  12. ^ Mauro Murzi "Rudolf Carnap (1891–1970)", Internet Encyclopedia of Philosophy, 12 Apr 2001.
  13. ^ Ayer, A.J. (1936). Language, Truth, and Logic (PDF). pp. 6–7.
  14. ^ "Ayer on the criterion of verifiability" (PDF). 29 November 2007. Retrieved 9 July 2023.
  15. ^ "Popper, Karl: Philosophy of Science | Internet Encyclopedia of Philosophy". Retrieved 2023-07-09.
  16. ^ a b c Malachi Haim Hacohen, Karl Popper: The Formative Years, 1902–1945: Politics and Philosophy in Interwar Vienna (Cambridge: Cambridge University Press, 2000), pp. 212–13.
  17. ^ a b "Popper's Account of Scientific Theories". Retrieved 2023-07-10.
  18. ^ Karl Popper, Science, & Pseudoscience: Crash Course Philosophy #8, retrieved 2023-07-10
  19. ^ Peter Godfrey-Smith, Theory and Reality: An Introduction to the Philosophy of Science (Chicago: University of Chicago Press, 2005), pp. 57–59.
  20. ^ James Fetzer, "Carl Hempel", in Edward N Zalta, ed, The Stanford Encyclopedia of Philosophy (Spring 2013): "However surprising it may initially seem, contemporary developments in the philosophy of science can only be properly appreciated in relation to the historical background of logical positivism. Hempel himself attained a certain degree of prominence as a critic of this movement. Language, Truth and Logic (1936; 2nd edition, 1946), authored by A. J. Ayer, offers a lucid exposition of the movement, which was—with certain variations—based upon the analytic/synthetic distinction, the observational/theoretical distinction, and the verifiability criterion of meaningfulness.

    Hempel (1950, 1951), meanwhile, demonstrated that the verifiability criterion could not be sustained. Since it restricts empirical knowledge to observation sentences and their deductive consequences, scientific theories are reduced to logical constructions from observables. In a series of studies about cognitive significance and empirical testability, he demonstrated that the verifiability criterion implies that existential generalizations are meaningful, but that universal generalizations are not, even though they include general laws, the principal objects of scientific discovery. Hypotheses about relative frequencies in finite sequences are meaningful, but hypotheses concerning limits in infinite sequences are not. The verifiability criterion thus imposed a standard that was too strong to accommodate the characteristic claims of science and was not justifiable".
  21. ^ Bruce Caldwell, Beyond Positivism: Economic Methodology in the 20th Century, rev edn (London: Routledge, 1994), pp. 47–48.
  22. ^ Samir Okasha, Philosophy of Science: A Very Short Introduction (New York: Oxford University Press, 2002) ch 5.
  23. ^ "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 likening 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. ... 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. Clearly, however, attributing foundationalist ambitions to the Circle as a whole constitutes a total misunderstanding of its internal dynamics and historical development, if it does not bespeak wilfull ignorance. At most, a foundationalist faction around Schlick can be distinguished from the so-called left wing whose members pioneered anti-foundationalism with regard to both the empirical and formal sciences" Thomas Uebel, "Vienna Circle", sec "3.3 Reductionism and foundationalism: Two criticisms partly rebutted", in Edward N Zalta, ed, The Stanford Encyclopedia of Philosophy (Summer 2012 edn).
  24. ^ a b c d Oswald Hanfling, ch 5 "Logical positivism", in Stuart G Shanker, Philosophy of Science, Logic and Mathematics in the Twentieth Century (London: Routledge, 1996), pp. 193–94.
  25. ^ Chapman, S. (2009). Logical positivism. In S. Chapman, & C. Routledge, Key ideas in linguistics and the philosophy of language. Edinburgh University Press. Credo Reference:
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