There are at least two theories as to the main evolutionary benefit of language. (This is not the best way of putting it, but I think it captures how I remember each side.) One side thinks that the big advantage of language is communication. With language you can discuss things with others and exchange contentful ideas. The other side thinks that language has nothing to do essentially with communication and it is rather mental organization that is the main benefit. Language use adds a large amount of structure to the mind and it is what enables us to have the abstract thoughts that we do and make long-term plans involving various contingent and hypothetical possibilities. The communication stuff is a happy accident of this. The latter position is defended by Chomsky and his followers. The prior position is defended by pretty much everyone else I think. There is a prima facie harmony between the views (as indicated by my comment following the second description). One view says language is for exchanging contentful messages and the other view says it is for having contentful thought. This meshes with the idea that language is used for putting into a public medium the content of one’s private thoughts. (That probably sounds quite naive and would not make partisans of either side happy.) I started thinking about whether there are any other possible pressures for the development of language or whether these two options exhaust the range of viable options. My initial instinct is that there should be more possibilities although I haven’t come up with them.

I had more thoughts about how to approach language use that may seem naive. One thread in the philosophy of language sees language, particularly semantics, as a logical phenomenon. Logic is the primary tool for investigating and understanding language. As Richard Montague put it, syntax, semantics and pragmatics (!!) are all mathematical phenomena. Another way of thinking about it is as a completely naturalistic phenomenon that arose in a species that developed under evolutionary pressure. Pressures that resulted in language development should have resulted in various processing limitations as well in order to be adaptationally useful. Continuing this idea: tools that are useful for understanding evolutionary development should be useful for understanding restrictions on languages, in particular, (getting into uncertain territory here) information theory, noisy-channel models, and models of redundancy. Thinking about it, it is kind of amazing that evolution ended up giving us logic, to put it one way.

One other thing that I feel gets left out of the logical models of language is the fact that while languages might have a logical basis of some kind, they also have a historical basis. They are entities (for the moment begging the question about the existence of public languages) that have developed in haphazard ways in response to various contingent, historical developments that could have easily gone other ways. There are words and phrases whose meanings have shifted over time and parts of languages whose syntax has changed dramatically. These elements are all thrown together, at least in languages that have live modern versions. These considerations make the idea of a single, synchronically pure language an idealization. That is to say, I’m not particularly surprised that we don’t have grammars for any natural language that generate all and only the sentences of that language.