Six of the Darśanas have received special prominence and are often called the six Orthodox Schools. They are the Nyâya and Vaiśeshika, Sâṅkhya and Yoga, Pûrva and Uttara Mîmâṃsâ, or Vedânta. The rest are either comparatively unimportant or are more conveniently treated of as religious sects. The six placed on the select list are sufficiently miscellaneous and one wonders what principle of classification can have brought them together. The first two have little connection with religion, though they put forward the emancipation of the soul as their object, and I have no space to discuss them. They are however important as showing that realism has a place in Indian thought in spite of its marked tendency to idealism.[738] They are concerned chiefly with an examination of human faculties and the objects of knowledge, and are related to one another. The special doctrine of the Vaiśeshika is the theory of atoms ascribed to Kaṇâda. It teaches that matter consists of atoms (aṇu) which are eternal in themselves though all combinations of them are liable to decompose. The Sâṅkhya and Yoga are also related and represent two aspects of the same system which is of great antiquity and allied to Buddhism and Jainism. The two Mîmâṃsâs are consecutive expositions of the teaching scattered throughout the Vedic texts respecting ceremonial and the knowledge of God respectively. The second Mîmâṃsâ, commonly called the Vedânta, is by far the more interesting and important. The common feature in these six systems which constitutes their orthodoxy is that they all admit the authority of the Veda. This implies more than our phrases revelation or inspiration of the Bible. Most of the Darśanas attach importance to the _pramâṇas_, sources or standards of knowledge. They are variously enumerated, but one of the oldest definitions makes them three: perception (pratyaksha), inference (anumâna) and scripture (śabda). The Veda is thus formally acknowledged to have the same authority as the evidence of the senses. With this is generally coupled the doctrine that it is eternal. It was not composed by human authors, but is a body of sound existing from eternity as part of Brahman and breathed out by him when he causes the whole creation to evolve at the beginning of a world period. The reputed authors are simply those who have, in Indian language, seen portions of this self-existent teaching. This doctrine sounds more reasonable if restated in the form that words are the expression of thought, and that if thought is the eternal essence of both Brahman and the soul, a similar eternity may attach to words. Some such idea is the origin of the Christian doctrine of the Logos, and in many religions we find such notions as that words have a creative efficacy,[739] or that he who knows the name of a thing has power over it. Among Mohammedans the Koran is supposed to be not merely an inspired composition but a pre-existing book, revealed to Mohammed piecemeal.