Verifiability principle
In the early twentieth century, the logical positivists put forth what came to be known as the verifiability theory of meaning. The verifiability theory was based upon the verifiability principle, which states: "A statement is literally meaningful (it expresses a proposition) if and only if it is either analytic or empirically verifiable." If it failed that test, then it was held by proponents of the verifiability principle to be literally meaningless—to be as a useless sound or babble. A.J. Ayer's famous book, Language, Truth, and Logic, was based on the verification principle, and presented a forceful and highly influential account of it.
David Hume (1711-1776) was a forerunner of the verification principle. He argued that all meaningful concepts depended on sense experience and/or basic "relations among ideas" (logical relations mostly, also mathematics); if something could not be traced back to one or the other of these then, he claimed, it was meaningless.
In Hume's famous words:
When we run over libraries, persuaded of these principles, what havoc must we make? If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: for it can contain nothing but sophistry and illusion. (Hume, "Enquiry Concerning Human Understanding," Section XII, Part III)
The logical positivists of the Vienna Circle (the so-called verificationists), used the verifiability principle or theory to build upon the theory of language that Ludwig Wittgenstein had introduced in his Tractatus Logico-Philosophicus.
The classification terms analytic/synthetic, especially as used by Immanuel Kant, have fallen into disuse in contemporary formal logic. (See the entry, "Analytic Proposition" for an account of this) In essence, the positivists equated Kant's synthetic statements with empirical knowledge. If an empirical statement is true, they claimed, it ought to be empirically verifiable, and if an empirical statement is false, it ought to be empirically falsifiable.
However, the verifiability principle itself is not empirically verifiable nor is it analytic. Thus the verifiability principle seems to be self-refuting. In the early days of the logical positivists (the members of the Vienna Circle and their followers (see the articles "Logical Posiitivism" and Vienna Circle"), this problem was not recognized. Later there were enormous efforts by logical positivists—Hempel, Carnap, and others—to develop a version of the verifiability principle that would withstand logical scrutiny and criticism, but those efforts always failed. Eventually those who wished to hold to to the verifiability principle could present it only as a recommendation, not as something that could be proved or supported with either logic or good argument.
The verifiability theory of meaning is also closely related to the correspondence theory of truth.
Bibliography
- Ayer, A.J., Language, Truth, and Logic. London: V. Gollancz (First ed., 1936; 2nd ed. rev. and enlarged, 1946).
- Hempel, Carl Gustav, Aspects of Scientific Explanation, and Other Essays in the Philosophy of Science. New York: Free Press (1965).
- Hume, David, ed. by Tom L. Beauchamp, An Enquiry Concerning Human Understanding. Oxford & New York : Oxford University Press (1999). ISBN 0198752490
- Sarkar, Sahotra, ed. with introd., Logical Empiricism at Its Peak: Schlick, Carnap, and Neurath. New York: Garland Pub. (1996).
See also
- Epistemic theories of truth
- Logical positivism
- Verificationist
- Hypothetico-deductive method
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