Quine (“Ontological Relativity”, “Two Dogmas”, and elsewhere) forcefully argued, to my mind convincingly, that matters of meaning are always matters of ontology. Theories of meaning (i.e. what ‘gavagai’ means) are theories of what there is. This is a view about semantics. I would like to extend it to syntax.
Think of syntactic categories as something like the pool of meanings that you get to pick from. In a sense, this is more than just a way of thinking about syntax. For every lexical item it is true that you have to pick between kinds of roles it can play. The translation is not direct, so let me make it more explicit. When we decide about meaning we modify our ontology. When we decide about syntactic category we modify our ontology, but also our metaphysical framework.
Take the following syntactic categories: verbs, nouns, transitive verbs, intransitive verbs, prepositional phrases, and sentence complements.
Now thinking about the following metaphysical categories: actions, objects, relations, causal relations, associations, properties and mental entities.
Do they fit together? It has been argued that, at some point in language development, children determine the content of words by using syntax. My guess is that what children do can also be well described by saying that children determine the content of words by using metaphysics. Take a new word ‘mem’ and its family ‘memming’, ‘memmed’ and ‘memmer’. It seems likely that children can connect the morphological and syntactic differences (those that come when the new word is used in sentences) by just using a simple metaphysical framework: words ending with ‘ing’ denote actions, some others with ‘ed’ denote properties, and those with appear by themselves, denote whole-objects. Furthermore, when sentences within sentences denote mental phenomena.
I guess one might say, but that’s just what syntax is. To which I would reply that that is just what metaphysics is. Of course, the important thing here is that, unlike a good part of the metaphysical tradition, we have very good empirical support now. Or, to put it somehow differently, this categorization is the product of the interaction of an organism with its environment. Metaphysics is not a given, experience independent knowledge. It’s rather more like something that we do, very often, and very naturally so. It could still be a priori, if by ‘a priori’ we don’t mean experience-independent, but rather data-independent. In this sense, ‘a priori’ would just mean ‘something that we do with theories and concepts’. But this requires a different text, one that might come later.
There is, still, another fight to be dwelt. And that is the developmental fight concerning cognition. I claim that all these metaphysical categories are present since early on in human cognition (experience) of the world. It has been shown that infants as young as 4 months of age already behave in accordance with the existence of objects, with their being solid and continuous in time, and with a good notion of what space and time is. Some, Elizabeth Spelke among them, want to follow Kant in claiming this to be a priori or given. Others follow Piaget in taking this as a contingent product of humans in the particular environment they live in. I tend to believe more in this second approach. Young infants, endowed with a powerful information processing system, one that is able to self-revise and self-modify (plasticity), come up with metaphysical categories that put some order to their experience. Through experience other more specific and powerful cognitive capacities, such as language (5 years of age, when fully competent) and logic (late adolescence) are developed.
In a sense, on this view, syntax (and with it language and logic) builds upon this metaphysic framework. The framework is general enough for infants to do it. Thus, the neural connections necessary for it to take place leave open space for various syntactic, lexical, pragmatic, moral, aesthetic and many other kinds of structures to be carved deeper, stronger, and more precisely in.