The Philosophy of the Upanishads c7.s1.7

c7.s1.7

That is to say—the Brahman, the power which presents itself to us materialised in all existing things, which creates, sustains, preserves, and receives back into itself again all worlds, this eternal infinite divine power is identical with the âtman, with that which, after stripping off everything external, we discover in ourselves as our real most essential being, our individual self, the soul. This identity of the Brahman and the âtman, of God and the soul, is the fundamental thought of the entire doctrine of the Upanishads. It is briefly expressed by the "great saying" tat tvam asi, "that art thou" (Chând. 6. 8. 7 f.); and aham brahma asmi, "I am Brahman" (Bṛih. 1. 4. 10). And in the compound word brahma-âtma-aikyam, "unity of the Brahman and the âtman," is described the fundamental dogma of the Vedânta system.