"The Over-soul" is an essay by Ralph Waldo Emerson, first published in 1841.

For Emerson the term denotes a supreme underlying unity which transcends duality or plurality, much in keeping with the philosophy of Advaita Vedanta. This non-Abrahamic interpretation of Emerson's use of the term is further supported by the fact that Emerson's Journal records in 1845 that he was reading the Bhagavad Gita and Henry Thomas Colebrooke's Essays on the Vedas. [2] Emerson goes on in the same essay to further articulate his view of this dichotomy between phenomenal plurality and transcendental unity:

We live in succession, in division, in parts, in particles. Meantime within man is the soul of the whole; the wise silence; the universal beauty, to which every part and particle is equally related, the eternal ONE. And this deep power in which we exist and whose beatitude is all accessible to us, is not only self-sufficing and perfect in every hour, but the act of seeing and the thing seen, the seer and the spectacle, the subject and the object, are one. We see the world piece by piece, as the sun, the moon, the animal, the tree; but the whole, of which these are shining parts, is the soul. [1]
Over-soul has more recently come to be used by Eastern philosophers such as Meher Baba and others as the closest English language equivalent of the Vedic concept of Paramatman.[3] (In Sanskrit the word param means "supreme" and atman means "soul"; thus Paramatman literally means "Supreme-Soul.") [1] The term is used frequently in discussion of Eastern metaphysics and has also entered western vernacular. In this context, the term "Over-soul" is understood as the collective indivisible Soul, of which all individual souls or identities are included. The experience of this underlying reality of the indivisible "I am" state of the Over-soul is said to be veiled from the human mind by sanskaras, or impressions, acquired over the course of evolution and reincarnation. Such past impressions form a kind of sheath between the Over-soul and its true identity, as they give rise to the tendency of identification with the gross differentiated body. Thus the world, as apperceived through the impressions of the past appears plural, while reality experienced in the present, unencumbered by past impressions (the unconditioned or liberated mind), perceives itself as the One indivisible totality, i.e. the Over-soul......from Wikipedia