4. Philosophy.--We have seen how both in the ritual system they administered and in the ideal they formed of the highest good, the Brahmans were led forward from the old ground of the Vedic nature-worship to a more inward and subjective religious attitude. The exaltation of Brahma, the power of prayer, to be the supreme god, was an advance from an external deity to a deity both external and present in man's own experience; and the appearance of a new way of salvation, though only permitted at first to the world-weary ascetic, in which inner contemplation and absorption could lead to the highest consummation of life, also showed that a new form of religion was at hand. In the philosophy of the Brahmanic period, the transition is made from the service of gods external to man, by the mechanism of rites, to the acknowledgment of a divine being with whom man feels himself to be inwardly akin and to whom he draws near by his own spiritual effort. In this movement, to which we learn that members of the lay aristocracy and even women of intellectual distinction made important contributions, and which may have appeared in its beginnings as a sceptical revolt against their own system, the Brahmans yet took part, and the works in which the record of it is contained became a part of revelation. The "Upanishads" or "communicated doctrines," form the third branch of the sacred knowledge, and much of this literature belongs to the period before Buddhism. These books are read still by the educated Hindu as part of scripture, and the philosophy of them is a part of his religion. We can only point out the principal terms and notions of that philosophy.