At the heart of Advaita Vedanta lies Brahman—the ultimate, unchanging, infinite reality that is existence itself. Unlike a creator God standing apart from creation, Brahman is both the efficient cause (nimitta karana) and material cause (upadana karana) of everything. The Upanishads describe Brahman through positive attributes as Sat-Chit-Ananda (Existence-Consciousness-Bliss): Sat means pure being, that which eternally IS; Chit signifies consciousness, self-luminous awareness requiring no external light; Ananda represents infinite fullness and bliss, complete unto itself. Yet Brahman ultimately transcends even these descriptions. The Mandukya Upanishad teaches that Brahman is "not conscious of the internal world, not conscious of the external world, not conscious of both worlds, not a mass of consciousness, not consciousness, not unconsciousness"—a via negativa pointing to what lies beyond conceptual categories. Nirguna Brahman (Brahman without attributes) cannot be objectified, spoken about, or mentally grasped. It can only BE, as the very self of the one seeking it.