—Compositionality is satisfied. This will bear emphasis later. I’m going to argue that, of the various ‘inferential role’ theories of concepts, only the one that says that concepts are definitions meets the compositionality condition. Sufficeit for now that words/concepts do contribute their definitions to the sentences/thoughts that contain them; it’s partand parcel of ‘bachelor’ meaning unmarried man that the sentence ‘John is a bachelor’ means John is an unmarried man anddoes so because it has ‘bachelor among its constituents. To that extent, at least, definitions are in the running to beboth word meanings and conceptual contents.
—Learnability is satisfied. If the concept DOG is a definition, then learning the definition should be all that’s required to learn the concept. A fortiori, concepts that are definitions don’t have to be innate.
To be sure, learning definitions couldn’t be the whole story about acquiring concepts. Not all concepts could be definitions, since some have to be the primitives that the others are defined in terms of; about the acquisition of theprimitive concepts, some quite different story will have to be told. What determines which concepts are primitive wasone of the questions that definition theories never really resolved. Empiricists in philosophy wanted the primitiveconcepts to be picked out by some epistemological criterion; but they had no luck in finding one. (For discussion ofthese and related matters, see Fodor 1981a, 1981 b.) But, however exactly this goes, the effect of supposing that thereare definitions is to reduce the problems about concepts at large to the corresponding problems about primitiveconcepts. So, if some (complex) concept C is defined by primitive concepts c, c2, . . . , then explaining how we acquireC reduces to explaining how we acquire c, c2, . . . And the problem of how we apply C to things that fall under itreduces to the problem of how we apply c, c2, . . . to the things that fall under them. And explaining how we reasonwith C reduces to explaining how we reason with c, c2, . . . And so forth. So there is good work for definitions to do ifthere turn out to be any.
All the same, these days almost nobody thinks that concepts are definitions. There is now something like a consensus in cognitive science that the notion of a definition has no very significant role to play in theories of meaning. It is, to besure, a weakish argument against
definitions that most cognitive scientists don’t believe in them. Still, I do want to remind you how general, and how interdisciplinary, the collapse of the definitional theory of content has been. So, here are some reasons why definitionsaren’t currently in favour as candidates for concepts (/word meanings):
—There are practically no defensible examples of definitions; for all the examples we’ve got, practically all words (/ concepts) are undefinable. And, of course, if a word (/concept) doesn’t have a definition, then its definition can‘t be itsmeaning. (Oh well, maybe there’s one definition. Maybe BACHELOR has the content unmarried man. Maybe there areeven six or seven definitions; why should I quibble? If there are six or seven definitions, or sixty or seventy, that stillleaves a lot of words/concepts undefined, hence a lot of words/concepts of which the definitional theory of meaningis false. The OED lists half a million words, plus or minus a few.)
Ray Jackendoff has suggested that the reason natural language contains so few phrases that are definitionally equivalent to words is that there are “nondiscrete elements of concepts . . . [which] play a role only in lexical semantics and neverappear as a result of phrasal combination” (1992: 48). (I guess that “nondiscrete” means something like analogue oriconic..) But this begs the question that it‘s meant to answer, since it simply assumes that that there are contents that onlynondiscrete symbols can express. Notice that you don’t need nondiscrete symbols to express nondiscrete properties. ‘Red’does quite a good job of expressing red. So suppose there is something essentially nondiscrete about the concepts thatexpress lexical meanings. Still, it wouldn’t follow that the same meanings can’t be expressed by phrases. So, even ifnondiscrete elements of concepts never appear as a result of phrasal combination, that still wouldn’t explain why mostwords can’t be defined.