Poetry begins as the divine speech of the bicameral mind. Then, as the bicameral mind breaks down, there remain prophets… conscious men now wrote and crossed out and careted and rewrote their compositions in laborious mimesis of the older divine utterances.
Jaynes argues that poetry originates as unmediated bicameral hallucination and degenerates into conscious literary craft only as the divine voices recede from the right hemisphere.
, The Origin of Consciousness in the Breakdown of the Bicameral Mind, 1976thesis