The Nyaya 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 Nyaya system.

The Nyaya Theory of Knowledge is the first systematic, critical. And comparative treatment of the Nyaya epistemology. It reveals how, as a thorough-going realistic view of the universe, the Nyaya 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.

The history of Indian Philosophy is a record of many different forms and types of philosophical thought. There is hardly any system in the history of Western philosophy which has not its parallel in one or other of the systems of Indian philosophy. But of the Indian systems, the Vedanta has received the greatest attention and it has sometimes passed as the only Indian system worth the name. This is but natural. The Vedanta with its sublime idealism has an irresistible appeal to the moral and religious nature of man. It has been, and will ever remain, a stronghold of spiritualism in life and philosophy. It is like one of "the great living wells, which keep the freshness of the eternal, and at which man must rest, get his breath, refresh himself." "The paragon of all monistic systems," says William James, " is the Vedanta philosophy of Hindustan." Although we have not such a sublime monism in the Nyaya, yet its contribution to philosophy is not really inferior in anyway. In fact, the other systems-the Vedanta not excepted -have been greatly influenced by its logical and dialectical technicalities. In their later developments all the systems consider the Naiyayika as the most powerful opponent and try to satisfy his objections. The understanding of their arguments and theories presupposes, therefore, the knowledge of the Nyaya.

As a system of realism, the Nyaya deserves special study to show that Idealism was not the only philosophical creed of ancient India. Then, as a system which contains a thorough refutation of the other schools, it should be studied before one accepts the validity of other views, if only to ascertain how far those view scan satisfy the acid test of the Nyaya criticisms and deserve to be accepted. But above all, as a through going realistic view of the universe, it supplies an important Eastern parallel to the triumphant modern Realism of the Vest, and contains the anticipations as well as possible alternatives of many contemporary realistic theories. The importance of the Nyaya is, therefore, as great for the correct understanding of ancient Indian philosophy, for the evaluation of modern western philosophy.

The theory of knowledge is the most important part—in fact, the very foundation of the Nyaya system. This book is an attempt to give a complete account of the Nyaya theory of knowledge. It is a study of the Nyaya theory of knowledge in comparison with the rival theories of other systems, Indian and western, and a critical estimation of its worth. Though theories of knowledge of the Vedanta and other schools have been partially studied in this way by some, there has as yet been no such systematic, critical and comparative treatment of the Nyayaepistemology. The importance of such as study of Indian realistic theories of knowledge can scarcely be overrated in this modern age of Realism.

The scope of the book is limited to the history of the Nyaya philosophy beginning with the Nyaya-Sutra of Gautama and ending with the syncretic works of Annam Bhatta, Visvanatha and others. It does not, however, concern itself directly with the historical development of the Nyaya. There are ample evidences to show that Nyaya as an art of reasoning is much older than the Nyaya-Sutra. We find references to such an art under the names of Nyaya, and vakovakya in some of the early Upanisads like the chandogya. (vii. 1.2) and the Subala (ii). It is counted among the up ring as or subsidiary parts of the Veda (vide Caranovyuha, ii; Nydya-Sutra.-Vrtti 1.1.1). It is mentioned under the names of anviksiki and tarkasastra in some of the oldest chapters of the Mahabharata to (vide Sabha anusasana and santi parvas). We need not multiply such references. Those here given show that the Nyaya as an art or science of reasoning existed in India long before the time of Gautama, the author of the Nyaya Sutra. As a matter of fact, it has been admitted by Vatsyayana, Uddyotakara, Jayenta, Bhatta and others that Gautama was not so much the founder of the Nyaya as its chief exponent who first gave an elaborate and systematic account of an already existing branch of knowledge called nyaya in the form of sutras or aphorisms. It is in sutras that the Nyaya was developed into a realistic philosophy on a logical basis. What was so long mere logic or an art of debate became a theory of the knowledge of reality? It is for this reason that the present work is based on the Nyaya Sutra and its main commentaries.