The Nyaya system is only a development and complement of that of Kanada, its metaphysics and psychology being the same. Its specific character consists in its being a very detailed and acute exposition of formal logic. As such it has remained the foundation of philosophical studies in India down to the present day. Besides dealing fully with the means of knowledge, which it states to be perception, inference, analogy, and trustworthy evidence, it treats exhaustively of syllogisms and fallacies. It is interesting to note that the Indian mind here independently arrived at an exposition of the syllogism as the form of deductive reasoning. The text-book of this system is the Nyaya-sutra of Gotama. The importance here attached to logic appears from the very first aphorism, which enumerates sixteen logical notions with the remark that salvation depends on a correct knowledge of their nature. Neither the Vaiçeshika nor the Nyaya-sutras originally accepted the existence of God; and though both schools later became theistic, they never went so far as to assume a creator of matter. Their theology is first found developed in Udayanacharya's Kusumanjali, which was written about 1200 A.D., and in works which deal with the two systems conjointly. Here God is regarded as a "special" soul, which differs from all other individual eternal souls by exemption from all qualities connected with transmigration, and by the possession of the power and knowledge qualifying him to be a regulator of the universe. Of the eclectic movement combining Sankhya, Yoga, and Vedanta doctrines, the oldest literary representative is the Çvetaçvatara Upanishad. More famous is the Bhagavadgita in which the Supreme Being incarnate as Krishna expounds to Arjuna his doctrines in this sense. The burden of his teaching is that the zealous performance of his duty is a man's most important task, to whatever caste he may belong. The beauty and the power of the language in which this doctrine is inculcated, is unsurpassed in any other work of Indian literature.