In the vision of the Upanishads, Brahman is the ultimate, absolute reality that underlies and pervades all existence, yet is never merely one entity among others. It is described as the unchanging, eternal ground of being, the source from which all beings arise, by which they live, and into which they return. This reality is often characterized as Sat–Cit–Ānanda: pure existence, pure consciousness, and bliss—not in the sense of fleeting pleasure, but as the fullness and completeness of being itself. Brahman is thus not an object within the universe, but the very basis that makes the universe and all experience possible.

At the same time, the Upanishads insist that Brahman eludes all finite description. The method of *neti neti*—“not this, not this”—is used to negate every limited concept or attribute that the mind might impose, pointing to a reality beyond all names and forms. Brahman is said to be beyond subject and object, beyond time, space, and causation, and yet it is not a mere void; it is self-luminous consciousness, the witness of all experience that remains untouched by the changing play of phenomena. In this way, Brahman is both beyond all qualities (*nirguṇa*) and yet spoken of as manifesting through qualities (*saguṇa*) when approached as the ground and ruler of the cosmos.

A central teaching of the Upanishads is the identity of this ultimate reality with the innermost Self, Ātman. Mahāvākyas such as “Tat tvam asi” (“That thou art”) and “Aham brahmāsmi” (“I am Brahman”) declare that the deepest essence of the individual is not separate from the absolute. Liberation, or mokṣa, is nothing other than the direct realization of this non-duality, the recognition that what appears as the multiplicity of the world is, at root, one undivided Brahman. Thus the same reality is both immanent—pervading all beings as their inner Self—and transcendent, surpassing all empirical distinctions and limitations.

The Upanishads also portray Brahman as both the material and efficient cause of the universe, the substratum in which all names and forms arise and into which they dissolve. Everything that exists is said to be “indeed Brahman,” smaller than the smallest and greater than the greatest, at once the inner controller and the all-encompassing whole. To contemplate Brahman, therefore, is to reflect on the ground of existence, consciousness, and bliss that silently supports every moment of experience, while remaining ever free from the fluctuations of the world.