verificationism

Verificationism, or the verifiability theory of meaning, is a philosophy of language and epistemology associated with logical positivism. It holds that the meaning of a proposition consists in the method by which it could be verified. In its standard form, a sentence is cognitively meaningful only if it can be verified by experience or is tautologically true or analytically necessary; otherwise it is non-cognitive or meaningless.

Origins and key figures: The doctrine emerged with the Vienna Circle in the 1920s and 1930s, with Rudolf Carnap, Moritz Schlick, Otto Neurath and others developing logical positivism. In the English-speaking world, A. J. Ayer popularized verificationism in Language, Truth and Logic (1936). Carnap distinguished observational language from theoretical language and sought a scientific language whose sentences are empirically testable and thereby meaningful.

Criticisms and decline: The verification principle itself cannot be empirically verified, which undermines its status as a criterion of meaning. Philosophers such as W. V. Quine challenged the analytic-synthetic distinction and highlighted how scientific theories revise meanings under changing evidence. Karl Popper offered a different demarcation criterion based on falsifiability rather than verifiability. By the mid-20th century, the program faced serious criticisms and gradually receded from the mainstream, though it left a lasting influence on philosophy of science and semantics.

Legacy: Although not upheld as a strict doctrine today, verificationism shaped debates about the meaning of scientific terms, the role of observation in theory choice, and the boundary between science and metaphysics. It spurred developments in empiricism, linguistic analysis, and the view that non-empirical assertions (ethics, aesthetics, religion) are expressive rather than cognitive.