Gyorgy Tamas works in the philosophy of logic, that difficult interdisciplin­ ary region wherein the notion of categories is both basic and subtle. To understand ways of thinking, to understand patterns of whatever is real, to recognize what is possible and to reject the nonsensical and the impossible is to comprehend the categories. This was a in thought and in fact, recurring motive of European thought from the earliest self-aware beginnings, and Tamas knows that history well, as his critical respect demonstrates. Ancient, medieval, and modern thinkers appear in this book, set forth in their own words; and likewise we see that Tamas has built upon the historians and commentators, upon the pioneering historical investigation of the categories by Trendelenburg a century ago and by Bochenski in our days. Tamas has two principal goals here: to investigate the logic, which is to say the structure and the relations, of the philosophical categories; and to set forth the logic of thought which may then be based upon the critically established system of categories obtained by that investigation. Ancillary but of striking value is his style of historical relevance which enables the reader to engage in a discussion that is both analytically sharp and developmentally insightful. Furthermore, Tamas draws upon his contem­ porary colleagues with similar critical respect: Lukasiewicz, Quine, Patzig, Menne, Tavanets and others.