Tweed, the PhD is a Doctor of Philosophy degree which you can earn in any of a wide array of fields, e.g., English Literature, Physics, Mathematics, Geology, Psychology, Musicology, Political Science, and, yes, in Philosophy. Philosophy is a field of study which literally means "love of knowledge," and usually includes the study of such fields as logic, ethics, epistemology, philosophy of science, etc. Philosophy is usually distinguished from science in that the former is pretty much rational, whereas the latter is supposed to be based largely on controlled observation (e.g., experimentation), but the boundary between philosophy and science is not hard and fast. (Consider mathematics, for example.)

I hope I haven't made the issue muddier than ever.

~SWO~