
Rather than just harkening to behavioral psychology or brain biology, Jaynes presents his theory from the perspective of psycho-cultural history.
Going back to the the earliest writings and studying particularly the many early civilizations of the Near East, Jaynes came to the conclusion that most of the people in these archaic cultures were *not* subjectively conscious as we understand it today.
Jaynes provides extensive illustrations--ranging from Sumer, Ur, Babylon, Egyptian, Early Mycenean, Hebrew, and even Mayan and Asian cultures--that support his theory of the bicameral mind. But he mainly focuses on Mycenean (Greek) material--and it is this material which we will examine mostly in this post.
Jaynes bluntly declares "There is in general no consciousness in the ILIAD." Analyzing Homer's great epic, Jaynes came to the conclusion that the characters of the Trojan siege did not have conscious minds, no introspection, as we know it in the modern human. [Julian Jaynes, THE ORIGIN OF CONSCIOUSNESS IN THE BREAKDOWN OF THE BICAMERAL MIND, Houghton Mifflin Company, 1976, p. 69]
Whether Achilles or Agamemnon, there was no sense of subjectivity. Rather they were men whom the gods pushed about like robots. The gods sang epics through their lips. Jayne declares that these Iliadic heroes heard "voices," real speech and directions from the gods--as clearly as those diagnosed epileptic or schizophrenic today.
Jaynes stresses that the Iliadic man did not possess subjectivity as we do--rather "he had no awareness of his awareness of the world, no internal mind-space to introspect upon." This mentality of the Myceneans, Jaynes calls the bicameral mind. [Ibid, p. 75]
Now what was this bicameral mind? Jaynes briefly discusses brain biology--in that there are three speech areas, for most located in the left hemisphere. They are: (1) the supplemental motor cortex; (2) Broca's area; and (3) Wernicke's area. Jaynes focuses on Wernicke's area, which is chiefly the posterior part of the left temporal lobe. It is Wernicke's area that is crucial for human speech.
Pursuing the bicameral mind, Jaynes focuses on the corpus callosum, the major inter-connector between the brain's hemispheres. In human brains the corpus callosum can be likened to a small bridge, a band of transverse fibers, only slightly more than one-eighth of an inch in diameter. This bridge "collects from most of the temporal lobe cortex but particularly the middle gyrus of the temporal lobe in Wernicke's area." And it was this bridge that served as the means by which the "gods" who dwelled in one hemisphere of the human brain were able to give "directions" to the other hemisphere. It is like thinking of the "two hemispheres of the brain almost as two individuals." Hence the bicameral mind! [Ibid, p. 117]
Archaic humans were ordered and moved by the gods through both auditory hallucinations and visual hallucinations. The gods mainly "talked" to them--but sometimes "appeared," such as Athene appeared to Achilles. And "when visual hallucinations occur with voices, they are merely shining light or cloudy fog, as Thetis came to Achilles or Yahwey to Moses." [Ibid, p. 93]
Jaynes believes in the mentality of the early Mycenean that volition, planning and initiative were literally organized with no consciousness whatsoever. Rather such volition was "told" to the individual--"sometimes with the visual aura of a familiar friend or authority figure or 'god,' or sometimes as a voice alone." [Ibid, p. 75]

Jaynes contests that such theocracies were the only means for a bicameral civilization to survive. Circumventing chaos, these rigid hierarchies allowed for "lesser men hallucinating the voices of authorities over them, and those authorities hallucinating yet higher ones, and so" to kings and gods. [Ibid, p. 79]
According to Julian Jaynes, "the idols of a bicameral world are the carefully tended centers of social control, with auditory hallucinations instead of pheromones."