From a tightly constrained definition of human consciousness, Jaynes offers a wealth of archeological and historical evidence to build his thesis. A novel idea even now, Jaynes proposed that until about 3 000 years ago, the human mind was sharply divided - a "bicameral mind." One part dealt with the normal daily occupations of survival and reproduction. The other part was a conduit for communications with the gods. Jaynes portrays the brain's structure and how it might generate "hallucinatory" voices and images that were construed as supernatural. Not until the civilization of Greece was well advanced did the consciousness we're familiar with arise and partially replace these hallucinatory visions. The pivot point, in Jaynes' view, is the distinction between the Iliad and Odyssey.
According to Jaynes, these two epic poems are qualitatively distinct, with the Iliad expressing the voice of the gods, but the Odyssey shifting to the voice of men. He makes bold assertions, "there is no general consciousness in the Iliad" - presuming the reader has accepted his definition of "consciousness." He dissects the poem in demonstrating it presents only the voices of the gods. By the conclusion of his analysis you may be convinced that if there really is such a thing as "genetic determinism" it certainly resided in the brain of humans who went through life without a single "conscious" expression. The brain created and imparted signals that could only be discerned as "divine." "Will" was absent. "Creativity" is missing from this analysis, although his sections on poetry and music make compelling reading. All was not lost for human beings, however. Conscious today, Jaynes finds in Homer's next poem the sign the evidence of its emergence. In the Odyssey, the humans take over the job of expressing their own destinies, leading to the expansion of consciousness through the remainder of history.
To accept this thesis, one must accept the idea that such human feats as irrigation systems in the Tigris-Euphrates civilizations, the Egyptian pyramids and even navigating the Mediterranean Sea were driven by hallucinations - "gods" imparted the means of these accomplishments. Jaynes urges this notion forcefully, citing examples in other societies such as the Aztecs or Incas of the Western Hemisphere [He ignores Asian societies utterly]. Even poetry and song, according to Jaynes, were actually the "voices" of hallucinations produced by the bicameral mind. The evolution to the "subjective" mind was rapid and clearly consequential, but Jaynes is unable to provide the mechanism of the transition.
Jaynes' proposal still generates discussion and assessment. Since tracing the evolution of the bicameral mind is inherently impossible, his proposal can never be verified. This book did, however, generate many studies. For that reason alone, this book remains a valuable contribution to cognitive studies. Whatever its shortcomings - the "reading in" of historical evidence, the over-precise time frame, the narrow European view, the bizarre speculations, don't invalidate the proposal of how the human mind evolved. No-one studying the mind and its development can afford to overlook Jaynes' contribution. [stephen a. haines, Ottawa, Canada]