Chemists in earlier centuries were quite interested in the nature of acids. They had no interest in analysing their concept of acid. After all, they knew that their understanding of acids was at a fairly primitive level, and what they wanted to do was understand something about the world better - the nature of acidity - not something about their own concepts.

17th century philosophers were not in a position to understand the mind as well as we can today, since the advent of experimental methods in psychology. It shows no disrespect for the brilliance of Descartes or Kant to acknowledge that the psychology which they worked with was primitive by comparison with what is available today in the cognitive sciences, any more than it shows disrespect for the brilliance of Aristotle to acknowledge that the physics he worked with does not compare with that of Newton or Einstein.

No one would suggest that we can adequately investigate what makes something an acid, or what makes something aluminum, by bringing our pretheoretical intuitions about these things into reflective equilibrium by way of armchair theorising.

The idea that we should check on our unreflective belief acquisition sounds great, but we need to know whether the processes of reflection which we put to work serves to improve our reliability or not.

I don't know whether I can say that having a career in philosophy has turned out as I imagined, since in many ways I had little idea of what such a life would be like. But philosophy is still tremendously exciting to me, and the opportunity to think, and talk, and write about these issues has been wonderful.

I do realise that talk of natural kinds dates back to Aristotle, but I'd better not say too much about ancient philosophers lest I be convicted of practicing history of philosophy without a license.

When I think about discussions at the Society for Philosophy and Psychology, a group which includes not only philosophers and psychologists, but also computer scientists and linguists, it is noteworthy that one can't always tell just from the content of particular contributions from the audience, whether a given questioner is a philosopher or an empirical scientist.