In philosophical writings about epistemology today there is a rather big to-do about internalist versus externalist accounts of knowledge. I'll define the distinction here speaking very roughly. To an internalist, I know X to be the case if and only if (a) X is the case, (b) I believe X, and (c) I have a good reason, or warrant, or justification, to believe X. To an externalist, on the other hand, I know X to be the case if and only if (a) X is the case, (b) I believe X, and (c) the reason why I believe X has an appropriate causal connection with X. The point of the labels is that justification (or whatever a particular theorist in this line may call it) is internal to my state of mind as the believer-of-X. Causation may be entirely external to my state of mind. Direct sense perception provides the simplest example. I form a belief that the leaves of this tree in front of me are green. It IS the case that they are green. The reason why I believe them...