The Upanishads approach the tension between unity and diversity by affirming a single, absolute reality called Brahman as the ground of all existence. Brahman is presented as infinite, unchanging being-consciousness, the one undivided reality in which all phenomena arise. The manifold world of names and forms (nāma-rūpa) is not denied, but is understood as a dependent appearance of this one substratum. Statements such as “sarvaṃ khalvidaṃ brahma” (“all this is indeed Brahman”) express the insight that every form, however diverse, is nothing other than Brahman in a particular configuration.

This metaphysical vision is deepened through the teaching that the innermost Self, Ātman, is identical with Brahman. Famous mahāvākyas such as “tat tvam asi” (“That thou art”) and “ahaṃ brahmāsmi” (“I am Brahman”) dissolve the apparent gulf between individual and cosmos. What seems to be a multitude of separate selves is, at the most fundamental level, the one Self appearing as many. The perception of radical separation is traced to avidyā, ignorance of this identity, which causes the many to be taken as ultimately real in themselves rather than as expressions of the One.

To articulate how the One can appear as many, the Upanishadic tradition employs the notion of māyā, the power or principle by which Brahman manifests as a diversified universe. This does not render the world a sheer non-entity, but situates it within a hierarchy of reality: relatively real at the empirical level, yet ultimately grounded in Brahman alone. The distinction between vyāvahārika-satya (practical or empirical truth) and pāramārthika-satya (absolute truth) allows diversity to be honored in lived experience while affirming that, from the highest standpoint, only non-dual Brahman truly is.

The texts illuminate this unity-in-diversity through vivid analogies. Just as many pots are nothing but clay in different shapes, or many ornaments are only gold in varied forms, so the countless entities of the world are Brahman under differing names and forms. The image of ocean and waves conveys the same intuition: waves arise, change, and subside, yet never cease to be water. Diversity, then, is a modification in designation and appearance, not in the underlying reality itself. Through contemplative insight into this structure of reality, the seeker comes to see that the apparent many are, at every point, the One shining through.