Ladies and gentlemen, the craziest theory on dreams since Freud,
Oneiric Darwinism found in Mark Blechner's book
The Dream Frontier.
I propose one more reason that we dream--to create new ideas, through partial random generation, which can then be retained if judged useful. . . . Dreams introduce random variations into psychic life and internal narratives. They produce "though mutations" Our minds can then select among these mutations and variations to produce new kinds of thought, imagination, self-awareness, and other psychic functions.
Dream interpretation as a science really begins in the late-eighteenth century with the publishing of several oneirocritics. Even though these early dream interpretation manuals were designed primarily as fortunetelling books, they represent an intersection between pre-modern beliefs of dreams being divine revelation and modern liberal epistemological structures (what we would call "science") that sought to define events as derivative of certain natural laws. By Freud's day, the divinity of dreams had been relegated to mere superstition, while the scientific explorations of dreaming had exploded.