The Nyãya philosophy is primarily concerned with the conditions of valid thought and the means of acquiring true knowledge of objects. Its ultimate end, like that of the other systems of Indian philosophy, is liberation-a state of pure existence- which is free from both pleasure and pain. For the attainment of this liberation, a true knowledge of objects is the surest means. Hence the theory of knowledge is the very foundation of the Nyãya system. The Nyãya Theory of Knowledge is the first systematic, critical and comparative treatment of the Nyãya epistemology. It reveals how, as a thorough-going realistic view of the universe, the Nyãya philosophy supplies an important Eastern parallel to the triumphant modern Realism of the West, and contains anticipations of as well as possible alternatives to many contemporary realistic theories. This book is important as much for the correct understanding of ancient Indian philosophy, as for the evaluation of modern Western philosophy.