In this book we have investigated aspects of the “five fundamental problems of biolinguistics”:

1. What constitutes knowledge of language?

2. How is this knowledge acquired?

3. How is this knowledge put to use?

4. What are the relevant brain mechanisms?

5. How does this knowledge evolve (in the species)?

As we have seen these comprise the classical questions asked about any biological system: (1) structure of the system, its function, and its use, (2) its development, and (3) its evolution. Our system of interest is language, so the areas pertinent to biolinguistics are (1) language, (2) development of language, and (3) evolution of language.

We have asked how the answers to these questions might be at least partially unified with each other and integrated into the natural sciences. We have argued that the evidence points toward a picture of unification in which there are a variety of cognitive systems, including language, each having its own specific properties and mechanisms. The available evidence appears to argue against the idea of a homogeneous and general purpose cognitive system designed to learn language, American history, and basket-weaving, or, as some would argue, even pigeon behavior.

We have also argued that the evidence for biolinguistics should include any and all relevant evidence. This is dictated by the constraint that scientific theories typically are radically underdetermined by evidence so we seek evidence wherever it is available. So, for example, in order to choose between particular formulations of a theory of English syntax, we can, and typically do, consider evidence from Japanese, Mohawk, Turkish, or any of the numerous other languages that have been investigated over the last forty years from the biolinguistic perspective.