Externalists reject any such view. I think that the idea that we can tell, simply by way of reflection, whether our beliefs are justified, is deeply commonsensical. More than that, the idea that responsible epistemic agents ought to reflect on their beliefs, and hold them only if they somehow pass muster, is utterly natural.

But there is no doubt that my own views on this are, in quite a number of ways, very different from those of Quine.

Bealer has a number of reasons for thinking that a naturalistic epistemology is self-undermining. Let me focus on one of these. (I've tried to take on all of them in the first chapter of Knowledge and Its Place in Nature.)

When I got to college, I planned to be a math major, and, in addition to signing up for some math courses, I decided to take some philosophy. Quite by chance, I took a philosophy of science course in which the entire semester was devoted to reading Locke's Essay. I was hooked. For the next few semesters, I took nothing but philosophy and math courses, and it wasn't long before I realised that it was the philosophy that really moved me.

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.

Rather, although belief may be adequate for explaining the behavior of individual animals - an animal which believes that p will behave no differently from an animal which knows that p - talk of knowledge is necessary once one begins to look at explaining the cognitive capacities of a species.

Here, there is simply no substitute for the kind of work that experimental psychologists do, work which shows some mechanisms to be quite reliable, and others to be quite unreliable.