Can we know anything for certain? There are those who think we can (traditionally labeled the "dogmatists") and those who think we cannot (traditionally labeled the "skeptics"). The theory of knowledge, or epistemology, is the great debate between the two. This book is an introductory and historically-based survey of the debate. It sides for the most part with the skeptics. It also develops out of skepticism a third view, fallibilism or critical rationalism, which incorporates an uncompromising realism about perception, science, and the nature of truth.