Looking at the advancement of thought in the @Rg-Veda we find first that a fabric of thought was gradually growing which not only looked upon the universe as a correlation of parts or aconstruction made of them, but sought to explain it as having emanated from one great being who is sometimes described as one with the universe and surpassing it, and at other times as being separate from it; the agnostic spirit which is the mother of philosophic thought is seen at times to be so bold as to express doubts even on the most fundamental questions of creation--"Who knows whether this world was ever created or not?" Secondly the growth of sacrifices has helped to establish the unalterable nature of the law by which the (sacrificial) actions produced their effects of themselves. It also lessened the importance of deities as being the supreme masters of the world and our fate, and the tendency of henotheism gradually diminished their multiple character and advanced the monotheistic tendency in some quarters. Thirdly, the soul of man is described as being separable from his body and subject to suffering and enjoyment in another world according to his good or bad deeds; the doctrine that the soul of man could go to plants, etc., or that it could again be reborn on earth, is also hinted at in certain passages, and this may be regarded as sowing the first seeds of the later doctrine of transmigration. The self (_atman_) is spoken of in one place as the essence of the world, and when we trace the idea in the Brahma@nas and the Ara@nyakas we see that atman has begun to mean the supreme essence in man as well as in the universe, and has thus approached the great Atman doctrine of the Upani@sads.