Edgar Allan Poe, in his poem "Dream within a Dream," depicts the poet standing on the "surf-tormented shore," contemplating a handful of sand, which is slipping through his fingers into the "pitiless wave." He weeps in the knowledge that he cannot save even a single grain from its extinction, and asks:
Is all that we see or seem
But a dream within a dream?
He questions the reality not only of the world constructed by individual consciousness but the very cosmic framework in which that microcosm resides. Not even Plato was that extreme. Yes, Poe was very, very far out. He was interested in other things besides homicidal orangutans. Check out his cosmological essay Eureka. He holds that the universe is, as it were, the fragmented mind and body of God, with all beings as "infinite individualizations of God." Ultimately the "Heart Divine" of God is our own; consciousness and the human soul are eternal, and each soul is in a sense its own creator and own God. Radicool!