The philosophical position that reality is fundamentally one - a single, unified substance or principle underlies all apparent diversity. This ancient insight, found across cultures from Vedantic non-dualism to Spinoza’s substance monism to Islamic Wahdat al-Wujud (unity of being), challenges everyday perception of separation and multiplicity.
At its core, monism dissolves the boundaries between subject and object, self and cosmos, matter and Consciousness. Where dualistic thinking creates categories and divisions, monistic philosophy recognizes these as conceptual overlays on an indivisible whole. The wave appears distinct from the ocean, yet remains inseparable from its source. This perspective reframes fundamental questions about identity, causation, and the nature of existence itself - suggesting that what we experience as separate entities are actually modifications or expressions of a singular reality.
Monism differs subtly from non-dualism, though the terms often overlap. Where monism positively asserts oneness as a metaphysical claim, non-dualism (Sanskrit: advaita, “not-two”) proceeds more apophatically - negating duality without necessarily affirming a single substance. The Perennial Philosophy recognizes both approaches as pointing toward the same fundamental insight: that the apparent multiplicity of existence emerges from and remains grounded in undifferentiated unity.
The implications cascade through multiple domains: in metaphysics, it collapses the creator-creation distinction; in epistemology, it suggests knower and known are ultimately one; in ethics, it grounds Compassion in literal rather than metaphorical unity. Whether approached through mysticism, philosophy, or science, monism points toward a reality more interconnected than our conceptual frameworks typically allow. The mystic who has passed through fana or realized moksha does not argue for monism but reports it - the convergent testimony of contemplative traditions suggesting this is less philosophical position than experiential recognition.
See also The One, Brahman, Spinoza, pantheism, substance, unity.