The term "Over-soul", such as in the writings of Ralph Waldo Emerson is understood to be 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 veiled from the human mind by impressions, acquired over the course of evolution and reincarnation. Such past impressions form a kind of sheath between the Over-soul and souls. These impressions give rise to the tendency of identification with the differentiated body. Thus the world, as perceived through the impressions of the past appears plural. 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.
Other explanations include Indira's Net.