Two Dogmas of Empiricism - Reductionism

Reductionism

Analyticity would be acceptable if we allowed for the verification theory of meaning: an analytic statement would be one synonymous with a logical truth, which would be an extreme case of meaning where empirical verification is not needed. "So, if the verification theory can be accepted as an adequate account of statement synonymy, the notion of analyticity is saved after all."

The problem that naturally follows is how statements are to be verified. An empiricist would say that it can only be done using empirical evidence. So some form of reductionism - "the belief that each meaningful statement is equivalent to some logical construct upon terms which refer to immediate experience" - must be assumed in order for an empiricist to 'save' the notion of analyticity. Such reductionism, says Quine, presents just as intractable a problem as did analyticity.

In order to prove that all meaningful statements can be translated into a sense-datum language, a reductionist would surely have to confront "the task of specifying a sense-datum language and showing how to translate the rest of significant discourse, statement by statement, into it." To illustrate the difficulty of doing so, Quine describes Rudolf Carnap's attempt in his book Der logische Aufbau der Welt.

Quine first observes that Carnap's starting point was not the strictest possible, as his "sense-datum language" included not only sense-events but also "the notations of logic, up through higher set theory... Empiricists there are who would boggle at such prodigality." Nonetheless, says Quine, Carnap showed great ingenuity in defining sensory concepts "which, but for his constructions, one would not have dreamed were definable on so slender a basis." However, even such admirable efforts left Carnap, by his own admission, far short of completing the whole project.

Finally, Quine objects in principle to Carnap's proposed translation of statements like "quality q is at point-instant x;y;z;t" into his sense-datum language, because he does not define the connective "is at". Without statements of this kind, it is difficult to see, even in principle, how Carnap's project could have been completed.

The difficulty that Carnap encountered shows that reductionism is, at best, unproven and very difficult to prove. Until a reductionist can produce an acceptable proof, Quine maintains that reductionism is another "metaphysical article of faith".