The Upanishads entered Western thought gradually, yet their central intuitions about Brahman, Atman, and māyā have left a deep imprint on both philosophy and spirituality. Western philosophers who were receptive to a single underlying reality found in Brahman a powerful analogue for monistic and idealist visions of the world. Schopenhauer, for instance, read the early translations and recognized in Brahman something akin to his own notion of the “Will,” while also sensing in māyā a resonance with the idea of the world as appearance. American Transcendentalists such as Emerson and Thoreau drew from these texts a sense of the unity of all life and the divinity immanent in nature, translating the Upanishadic insight “Ātman = Brahman” into the language of the Over-Soul and radical interiority. Through such figures, the Upanishads helped shape Western reflections on consciousness, identity, and the limits of purely material explanations of reality.

As these ideas circulated, they also nourished a range of modern spiritual movements that sought a more experiential, inward form of religiosity. The Theosophical Society turned to Upanishadic and Vedantic themes to articulate a vision of spiritual evolution, karma, and the soul’s journey toward union with an ultimate ground of being, thereby popularizing these concepts in new esoteric syntheses. Neo-Vedantic teachers such as Vivekananda, and later exponents of Advaita, presented non-dual readings of the Upanishads to Western audiences, emphasizing the divinity of the Self, the unity of all paths in Brahman, and the possibility of direct realization rather than mere belief. New Thought and New Age currents, along with many strands of contemporary nondual teaching, have taken up this language of inner divinity, consciousness as fundamental, and the illusory or provisional character of separateness, often weaving it together with practices of meditation, yoga, and self-inquiry.

Across these diverse appropriations, several Upanishadic motifs have become touchstones for seekers and thinkers alike. The affirmation of a single, all-pervading reality behind the flux of phenomena has encouraged Western explorations of non-dualism and the idea that consciousness is not merely a byproduct of matter. The teaching that the deepest Self is not ultimately separate from the Absolute has inspired both philosophical accounts of divine immanence and spiritual paths centered on recognizing one’s true nature. The emphasis on direct inner realization, coupled with the sense that ultimate truth eludes conceptual capture—evoked in the apophatic gesture of “not this, not this”—has reinforced a turn away from purely external authority toward contemplative, experiential insight. In this way, the Upanishads have served less as a foreign curiosity and more as a profound interlocutor, inviting Western philosophy and modern spirituality to reconsider what it means to know, to be, and to awaken.