Logical positivism

A 20th-century philosophical movement that sought to ground meaningful knowledge in logic and empirical verification, treating metaphysical claims as cognitively meaningless.

Verification principle: A criterion that ties a statement’s cognitive meaning to the possibility of verifying it through experience or logical analysis. It supplied the movement’s test for separating meaningful claims from metaphysics.
Vienna Circle: A group of philosophers and scientists in Vienna who met regularly in the 1920s and 1930s. Its members organized and publicized logical positivism as a collective philosophical program.
Metaphysics: The branch of philosophy that investigates reality’s most general features, including existence, identity, and causation. Logical positivists rejected many metaphysical assertions as lacking cognitive meaning.
A. J. Ayer: A British philosopher who popularized logical positivism in English through his book Language, Truth and Logic. His influential presentation made verificationism familiar beyond the Vienna Circle.
Analytic–synthetic distinction: The distinction between truths grounded in meanings or logic and claims that depend on facts about the world. It shaped how positivists separated logic from empirical knowledge.
Moritz Schlick: A German philosopher who led the Vienna Circle until his assassination in 1936. His seminars and leadership helped establish the Circle’s intellectual center.
Critical rationalism: Karl Popper’s philosophy of science, which treats falsifiability rather than verification as a key mark of scientific theories. Popper challenged verification as a workable boundary between science and non-science.
The Structure of Scientific Revolutions: Thomas Kuhn’s 1962 book arguing that scientific development includes paradigm shifts and periods of revolutionary change. Kuhn’s account challenged positivist pictures of science as cumulative and governed by fixed criteria.
Empiricism: The philosophical view that experience is the primary source or justification of knowledge about the world. Logical positivism turned empiricism into a program for scientific knowledge.
Rudolf Carnap: A German-born philosopher who developed influential accounts of logic, language, and scientific knowledge. His work gave the movement some of its most systematic formulations.

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