Graham Priest presents an exploration of Buddhist metaphysics, drawing on texts which include those of Nãgãrjuna and Dõgen. The development of Buddhist metaphysics is viewed through the lens of the catuṣkoṭi. At its simplest, and as it appears in the earliest texts, this is a logical/ metaphysical principle which says that every claim is true, false, both, or neither; but the principle itself evolves, assuming new forms, as the metaphysics develops. An important step in the evolution incorporates ineffability. Such things make no sense from the perspective of a logic which endorses the principles of excluded middle and non-contradiction, which are standard fare in Western logic. However, the book shows how one can make sense of them by applying the techniques of contemporary non-classical logic, such as those of First Degree Entailment, and Plurivalent Logic. An important issue that emerges as the book develops is the notion of non-duality and its transcendence. This allows many of the threads of the book to be drawn together at its end. All matters are explained, in as far as possible, in a way that is accessible to those with no knowledge of Buddhist philosophy or contemporary non-classical logic.

This book is simply beautiful. With its elegant cover art and comfortable size, it is a pleasure to look at, to hold, and to read. Moreover, Priest ... does a lovely job of tracing the evolution of Buddhism ... Highly recommended. * G. Wrisley, CHOICE *
The Fifth Corner of Four may be most suitable for an audience trained in the field of Philosophy rather than Buddhist Studies. * Ronald S. Green, Coastal Carolina University, Journal of Buddhist Ethics *

Graham Priest has held chairs in philosophy in Australia, the UK, and the USA, as well as visiting appointments in a number of other countries, including Germany and Japan. He is currently Distinguished Professor of Philosophy at the Graduate Center, City University of New York, and Boyce Gibson Professor Emeritus at the University of Melbourne. He is known for his work on non-classical logic, particularly in connection with dialetheism, on the history of philosophy, and on Buddhist philosophy. He has published articles in nearly every major philosophy and logic journal, and is the author of seven books, mostly with Oxford University Press.