Logical positivism

Logical positivism (later referred to as logical empiricism, rational empiricism, and also neo-positivism) is a philosophy that combines positivism with a version of apriorism.

It originated in the Vienna Circle in the 1920s, where Rudolf Carnap, Otto Neurath, et al. divided statements into those which are analytic (true a priori) and those which are synthetic (verified by sensory experience). This was perhaps presaged by Hume's fork. Logical positivism holds that philosophy should aspire to the same sort of rigor as science. Philosophy should provide strict criteria for judging sentences true, false and meaningless.

Examples of logical positivists include Moritz Schlick, Rudolf Carnap, Otto Neurath, Friedrich Waismann, John Dewey, Bertrand Russell, Neils Bohr and A.J. Ayer. Karl Popper is also often associated with the Vienna Circle, although he was never a member, and he went on to become a main critic of positivism's "verification" with his own "falsification" approach. Otto Neurath claimed that the most significant output produced by the logical positivist circle was the International Encyclopedia of Unified Science published by University of Chicago Press in 1938. Most of these authors contributed to this Encyclopedia.

Assertions and Origins of Logical Positivism

Although the logical positivists held a wide range of beliefs on many matters, they all shared an interest in science and deep skepticism of the theological and metaphysical. Following Wittgenstein, many subscribed to the correspondence theory of truth, although some, like Neurath, believed in coherentism. They believed that all knowledge should be based on logical inference from simple "protocol sentences" grounded in observable facts. Hence many supported forms of realism, materialism, philosophical naturalism, and empiricism.

The logical positivists were very much influenced by and were great admirers of the early Ludwig Wittgenstein (from the period of the Tractatus). Wittgenstein himself was not a logical positivist, although he was on friendly terms with many members of the Vienna Circle while in Vienna, especially fellow aristrocrat Moritz Schlick. However, Wittgenstein's relations were not entirely amicable after he left Vienna. While Wittgenstein worked mostly in cooperation for nearly a decade with Circle member Friedrich Waismann to impose form and structure on his often oracular utterances, using him as a secretary and speaking of cooperating on a book with him, when Waismann came to Cambridge in 1937 Wittgenstein barely acknowledged him.

Logical positivism is perhaps best known for the verifiability criterion of meaning, which asserts that a statement is meaningful if and only if it is empirically verifiable. One intended consequence of the verification criterion is that all non-empirical forms of discourse, including ethics and aesthetics, are not "literally" or "cognitively" meaningful, and so belong to "metaphysics".

Logical positivism was essential to the development of early analytic philosophy. It was disseminated throughout the European continent and, later, in American universities by the members of the Vienna Circle. A.J. Ayer is considered responsible for the spread of logical positivism to Britain. The term subsequently came to be almost interchangeable with "analytic philosophy" in the first half of the twentieth century. Logical positivism was immensely influential in the philosophy of language and represented the dominant philosophy of science between World War I and the Cold War. Many subsequent commentators on "logical positivism" have attributed to its proponents a greater unity of purpose and creed than they actually shared, overlooking the complex disagreements among the logical positivists themselves.

Criticisms

Critics of Logical Positivism say that its fundamental tenets could not themselves be formulated in a way that was clearly consistent. The verifiability criterion of meaning did not seem verifiable; but neither was it simply a logical tautology, since it had implications for the practice of science and the empirical truth of other statements. This presented severe problems for the logical consistency of the theory. Another problem was that, while positive existential claims (There is at least one human being) and negative universals (Not all ravens are black) allow for clear methods of verification (find a human or a non-black raven), negative existential claims and positive universal claims do not.

Universal claims could apparently never be verified: How can you tell that all ravens are black, unless you've hunted down every raven ever, including those in the past and future? This led to a great deal of work on induction, probability, and "confirmation," (which combined verification and falsification; see below).

Karl Popper, a well known critic of Logical Positivism, published the book Logik der Forschung (Eng.:The Logic of Scientific Discovery) in 1934. In it he presented an influential alternative to the verifiability criterion of meaning, defining scientific statements in terms of falsifiability. First, though, Popper's concern was not with distinguishing meaningful from meaningless statements, but distinguishing scientific from metaphysical statements. He did not hold that metaphysical statements must be meaningless; neither did he hold that a statement that in one century was metaphysical, while unfalsifiable (like the ancient Greek philosophy about atoms), could not in another century become falsifiable, and thus scientific (by the 20th century atoms would become part of science). About psychoanalysis he thought something similar: in his day it offered no method for falsification, and thus was not falsifiable and not scientific, but he didn't exclude it being meaningful, nor did he say psychoanalysts were necessarily wrong (it only couldn't be proven either way: that would have meant it was falsifiable), nor did he exclude that one day psychoanalysis could evolve into something falsifiable, and thus scientific. He was, in general, more concerned with scientific practice than with the logical issues that troubled the positivists. Second, although Popper's philosophy of science enjoyed great popularity for some years, if his criterion is construed as an answer to the question the positivists were asking it turns out to fail in exactly parallel ways. Negative existential claims (There are no unicorns) and positive universals (All ravens are black) can be falsified, but positive existential and negative universal claims cannot.

Logical positivists' response to the first criticism is that Logical Positivism, like all other philosophies of science, is a philosophy of science, not an axiomatic system that can prove its own consistency (see Gödel's incompleteness theorem). Secondly, a theory of language and mathematical logic were created to answer what it really means to say things like "all ravens are black".

A response to the second criticism was provided by A. J. Ayer in Language, Truth and Logic, in which he sets out the distinction between 'strong' and 'weak' verification. "A proposition is said to be verifiable, in the strong sense of the term, if, and only if, its truth could be conclusively established by experience." (Ayer 1946:50) It is this sense of verifiable that causes the problem of verification with negative existential claims and positive universal claims. However, the weak sense of verification states that a proposition is "verifiable... if it is possible for experience to render it probable." (ibid) After establishing this distinction, Ayer goes on to claim that "no proposition, other than a tautology, can possibly be anything more than a probable hypothesis" (Ayer 1946:51) and therefore can only be subject to weak verification. This defence was controversial among Logical Positivists, some of whom stuck to strong verification, and claimed that general propositions were indeed nonsense.

Subsequent philosophy of science tends to make use of the better aspects of both of these approaches. Work by W. V. O. Quine and Thomas Kuhn has convinced many that it is not possible to provide a strict criterion for good or bad scientific method outside of the science we already have. But even this sentiment was not unknown to the logical positivists: Otto Neurath famously compared science to a boat which we must rebuild on the open sea.

See also

• Kurt Gödel
• Rudolf Carnap
• Moritz Schlick
• Otto Neurath
• David Stove

• Sociological positivism

External links

• http://www.philosophypages.com/hy/6q.htm
• Logik der Forschung in 1934
• The Philosophy of Logical Positivism

References

ISBN links support NWE through referral fees

• Edmonds, David & Eidinow, John; Wittgenstein's Poker, ISBN 0066212448
• Ayer, A. J.; Language, Truth and Logic, ISBN 0486200108
• Neurath, Otto, and Carnap, R et. al. 1938. International Encyclopedia of Unified Science, U. Chicago Press., Chicago.

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