What is "logical positivism"

n. (context philosophy English) A 20th century school of philosophy which held that all knowledge is based on logical inferences from empirical observations.

n. the form of empiricism that bases all knowledge on perceptual experience (not on intuition or revelation) [syn: positivism]

Logical positivism and logical empiricism, which together formed neopositivism, was a movement in Western philosophy that embraced verificationism, an approach that sought to legitimize philosophical discourse by placing it on a basis shared with empirical sciences' best examples, such as Einstein's general theory of relativity. In the verificationist theory of knowledge, only statements verifiable either by deductive logic or direct observation would be cognitively meaningful. Efforts to convert philosophy to this new scientific philosophy were intended to prevent confusion rooted in unclear language and unverifiable claims. The Berlin Circle and the Vienna Circle—groups of philosophers, scientists, and mathematicians in Berlin and in Vienna—propounded logical positivism starting in the late 1920s.

Logical positivists culled from Ludwig Wittgenstein's early philosophy of language the verifiability principle or criterion of meaningfulness. As in Ernst Mach's phenomenalism, whereby the mind can know only actual or potential sensory experience, verificationists took all sciences' basic content to be only sensory experience. And some influence came from Percy Bridgman's musings that others proclaimed as operationalism, whereby a physical theory is understood by what laboratory procedures scientists perform to test its predictions. In verificationism, only the verifiable was scientific, and thus meaningful (or cognitively meaningful), whereas the unverifiable, being unscientific, was meaningless "pseudostatements" (just emotively meaningful). Unscientific discourse, as in ethics and metaphysics, would be unfit for discourse by philosophers, newly tasked to organize knowledge, not develop new knowledge.

Logical positivism is sometimes stereotyped as forbidding talk of unobservables, such as microscopic entities or such notions as causality and general principles, but that is an exaggeration. Rather, most neopositvists viewed talk of unobservables as metaphorical or elliptical: direct observations phrased abstractly or indirectly. So theoretical terms would garner meaning from observational terms via correspondence rules, and thereby theoretical laws would be reduced to empirical laws. Via Bertrand Russell's logicism, reducing mathematics to logic, physics' mathematical formulas would be converted to symbolic logic. And via Russell's logical atomism, ordinary language would break into discrete units of meaning. Rational reconstruction, then, would convert ordinary statements into standardized equivalents, all networked and united by a logical syntax. A scientific theory would be stated with its method of verification, whereby a logical calculus or empirical operation could verify its falsity or truth.

In the late 1930s, logical positivists fled Germany and Austria for Britain and United States. By then, many had replaced Mach's phenomenalism with Otto Neurath's physicalism, whereby science's content is not actual or potential sensations, but instead is entities publicly observable. And Rudolf Carnap, who had sparked logical positivism in the Vienna Circle, had sought to replace verification with simply confirmation. With World War II's close in 1945, logical positivism became milder, logical empiricism, led largely by Carl Hempel, in America, who expounded the covering law model of scientific explanation. Logical positivism became a major underpinning of analytic philosophy, and dominated Anglosphere philosophy, including philosophy of science, while influencing sciences, but especially social sciences, into the 1960s. Yet the movement failed to resolve its central problems, and its doctrines were increasingly criticized, most trenchantly by W. V. O. Quine, Norwood Hanson, Karl Popper, Thomas Kuhn, and Carl Hempel.