In this book I present what seem to me (at the moment) to be right an swers to some of the main philosophical questions about the topics men tioned in the title, and I argue for them where I can. I hope that what I say may be of interest both to those who have already studied these ques tions a lot and to those who haven't. There are several important topics in epistemology to which I give little or no attention here - such as the nature of a proposition, the major classifications of propositions (neces sary and contingent, a priori and a posteriori, analytic and synthetic, general and...