—It’s a general problem for theories that seek to construe content in terms of inferential role, that there seems to be no way to distinguish the inferences that constitute concepts from other kinds of inferences that concepts enter into. Thepresent form of this general worry is that there seems to be no way to distinguish the inferences that define conceptsfrom the ones that don’t. This is, of course, old news to philosophers. Quine shook their faith that ‘defining inference’is well defined, and hence their faith in such related notions as analyticity propositions true in virtue of meaning alone,and so forth. Notice, in particular, that there are grounds for scepticism about defining inferences even if you suppose(as, of course, Quine does not) that the notion of necessary inference is secure. What’s at issue here is squaring thetheory of concept individuation with the theory of concept possession. If having a concept requires accepting theinferences that define it, then not all necessities can be definitional. It is, for example, necessary that 2 is a primenumber; but surely you can have the concept 2 and not have the concept of a prime; presumably there were millenniawhen people did. (Similarly, mutatis mutandis, for the concept WATER if it’s necessary that water is H2O. I’ll come backto this sort of point in Chapter 4.)
It is often, and rightly, said that Quine didn’t prove that you can’t make sense of analyticity definition, and the like. But so what? Cognitive science doesn’t do proofs; it does empirical, non-demonstrative inferences. We have, as things nowstand, no account of what makes an inference a defining one, and no idea how such an account might be devised.That’s a serious reason to suppose that the theory of content should dispense with definitions if it can.
—Although in principle definitions allow us to reduce all sorts of problems about concepts at large to corresponding problems about concepts in the primitive basis (see above), this strategy quite generally fails in practice. Even if thereare definitions, they seem to play no very robust role in explaining what happens when people learn concepts, or whenthey reason with concepts, or when they apply them. Truth to tell, definitions seem to play no role at all.
For example, suppose that understanding a sentence involves recovering and displaying the definitions of the words that the sentence contains. Then you would expect, all else equal, that sentences that contain words with relativelycomplex definitions should be harder to understand than sentences that contain words with relatively simpledefinitions. Various psychologists have tried to get this effect experimentally; to my knowledge, nobody has eversucceeded. It‘s an iron law of cognitive science that, in experimental environments, definitions always behave exactly asthough they weren’t there.
In fact, this is obvious to intuition. Does anybody present really think that thinking BACHELOR is harder than thinking UNMARRIED? Or that thinking FATHER is harder than thinking PARENT? Whenever definition is bygenus and species, definitional theories perforce predict that concepts for the former ought to be easier to think thanconcepts for the latter. Intuition suggests otherwise (and so, by the way, do the experimental data; see e.g. Paivio 1971).
Hold-outs for definitions often emphasize that the experimental failures don’t prove that there aren’t any definitions. Maybe there’s a sort of novice/expert shift in concept acquisition: (defining) concepts like UNMARRIED MAN get‘compiled’ into (defined) concepts like BACHELOR soon after they are mastered. If experiments don’t detectUNMARRIED MAN in ‘performance’ tasks, maybe that’s because
BACHELOR serves as its abbreviation.27 Maybe. But I remind you, once again, that this is supposed to be science, not philosophy; the issue isn’t whether there might be definitions, but whether, on the evidence, there actually are some.Nobody has proved that there aren’t any little green men on Mars; but almost everybody is convinced by repeatedfailures to find them.
Much the same point holds for the evidence about concept learning. The (putative) ontogenetic process of compiling primitive concepts into defined ones surely can’t be instantaneous; yet developmental cognitive psychologists find noevidence of a stage when primitive concepts exist uncompiled.Jean-marc pizano