The unity of existence is one of the great themes of Vedanta and an essential pillar of its philosophy. Unity is the song of life; it is the grand theme underlying the rich variations that exist throughout the cosmos. Whatever we see, whatever we experience, is only a manifestation of this eternal oneness.

The divinity at the core of our being is the same divinity that illumines the sun, the moon, and the stars. There is no place, where we do not exist. “The Self is everywhere,” says the Isha Upanishad. “Whoever sees all beings in the Self, and the Self in all beings, hates none. For one who sees oneness everywhere, how can there be delusion or grief?”

All fear and all misery arise from our sense of separation from the great cosmic unity; the web of being that enfolds us. “There is fear from the second,” says the Brihadaranyaka Upanishad. Duality, our sense of separation from the rest of creation, is always a misperception since it implies that something exists other than God. There can be no other.

“This grand preaching, the oneness of things, making us one with everything that exists, is the great lesson to learn,” said Swami Vivekananda a century ago. The Self is the essence of this universe, the essence of all souls. You are one with this universe.

He, who says he is different from others, even by a hair’s breadth, immediately becomes miserable. Happiness belongs to him who knows this oneness, who knows he is one with

this universe. — Vedanta.org