Logical positivism

The core idea

Logical positivism grew out of the Vienna Circle, a group of scientists and philosophers including Moritz Schlick, Rudolf Carnap and Otto Neurath, who met in the 1920s and 30s. Inspired by modern logic, by Bertrand Russell and by their reading of Ludwig Wittgenstein's Tractatus, they aimed to clear away metaphysics.

Their weapon was verificationism: a statement has meaning only if it is true by definition or can be checked by experience. Statements about God, the Absolute or objective values fail the test, so they are neither true nor false but meaningless. A. J. Ayer's Language, Truth and Logic (1936) brought these ideas to English readers and argued that moral statements merely express feelings.

What they hold

• Meaningful statements are either true by definition or empirically verifiable.
• Traditional metaphysics is meaningless rather than false.
• Philosophy's job is the logical clarification of science.
• Moral and aesthetic statements express attitudes rather than facts.

The main criticisms

The decisive objection was that the verification principle fails its own test: it is neither true by definition nor verifiable by experience. Karl Popper argued that falsifiability, not verifiability, marks science, and W. V. O. Quine attacked the distinction between truths of meaning and truths of fact. By the 1960s the movement had largely dissolved, though its standards of clarity shaped analytic philosophy.

“Whereof one cannot speak, thereof one must be silent.”

Ludwig Wittgenstein, Tractatus 7, trans. C. K. Ogden

Further reading

• EncyclopediaStanford Encyclopedia of Philosophy: Logical Empiricism
• WikipediaLogical positivism