This text stresses the importance of Hume's An Inquiry Concerning Human Understanding not only as a philosophical text in its own right, but also as a starting point for developing an understanding of broader philosophical issues. Taking in such thinkers as Pierce, Wittgenstein, Frege and Ryle, the book is written as a companion volume to the Inquiry. First published in 1961, this is a reprint of the corrected 1966 edition.