I have been reading it (and rereading it) for the last 3 months (almost 4 now).
Jaynes, a Princeton psychologist, posits that there is an evolution in the human mind...one in which early man (before 3,000 years ago) was not conscious at all and in fact had a bicameral brain such that the non-dominant hemisphere was completely devoted to vocal transmissions from the "gods."
I have still not finished the book but Jaynes has yet to define who these "gods" are.
That said, he does base his theory on meticulous research (based on ancient human literature like the Iliad, the Odyssey, the Epic of Gilgamesh, the Bible and the mountain of archaeological evidence).
In the end, he suggests that over that vast span of time from 3,000 BC and before TO the present, the human mind has evolved from hearing and acting upon hallucinated voices to acting upon its own empirical reasoning. And this has occurred not without a deep longing for that earlier time when authorization came from hallucinated voices.
The transition was possibly from a time of direct communication (such as in the Garden of Eden) to hallucinations with the gods in the Iliad to the development of human consciousness. During that evolution, there were shifts that included the prophets, the oracles, possession (demonic and otherwise) and, in our contemporary world, schizophrenic voices.
Jaynes most creatively posits that a major part of what Jesus/Yeshua accomplished (aside from our salvation) was a rebirth of the bicameral voices--this time the voice of the Holy Spirit.
This premise would complete the circle.
In Eden, the Fall of Man meant the loss of direct communication with the Creator...but, with our Salvation, such contact was reestablished via the bicameral reception of the voice of God via the HS.
Here are some of the reviews of this book (from JulianJaynesSociety.com)...
"This book and this man's ideas may be the most influential, not to say controversial, of the second half of the twentieth century. I cannot recommend the book emphatically enough. I have never reviewed a book for which I had more enthusiasm. . . . It renders whole shelves of books obsolete." − William Harrington, in The Columbus Dispatch"[Jaynes] has one of the clearest and most perspicuous defenses of the top-down approach [to consciousness] that I have ever come across." − Daniel Dennett, Ph.D., Professor of Philosophy, Tufts University, in Brainchildren
"The weight of original thought in it is so great that it makes me uneasy for the author's well-being: the human mind is not built to support such a burden." − David C. Stove, Ph.D. (1927-1994), Professor of Philosophy, University of Sydney
"Julian Jaynes's theories for the nature of self-awareness, introspection, and consciousness have replaced the assumption of their almost ethereal uniqueness with explanations that could initiate the next change in paradigm for human thought." − Michael A. Persinger, Ph.D., Professor of Behavioral Neuroscience, Laurentian University, in Reflections on the Dawn of Consciousness
"Having just finished The Origin of Consciousness, I myself feel something like Keats' Cortez staring at the Pacific, or at least like the early reviewers of Darwin or Freud. I'm not quite sure what to make of this new territory; but its expanse lies before me and I am startled by its power." − Edward Profitt, in Commonweal
"Neuroimaging techniques of today have illuminated and confirmed the importance of Jaynes' hypothesis." − Robert Olin, M.D., Ph.D., Professor Emeritus in Preventive Medicine, in Lancet
"The bold hypothesis of the bicameral mind is an intellectual shock to the reader, but whether or not he ultimately accepts it he is forced to entertain it as a possibility. Even if he marshals arguments against it he has to think about matters he has never thought of before, or, if he has thought of them, he must think about them in contexts and relationships that are strikingly new." − Ernest R. Hilgard, Ph.D. (1904-2001), Professor of Psychology, Stanford University
"When Julian Jaynes...speculates that until late in the second millennium B.C. men had no consciousness but were automatically obeying the voices of gods, we are astounded but compelled to follow this remarkable thesis through all the corroborative evidence..." − John Updike, in The New Yorker
"Some of Jaynes' original ideas may be the most important of our generation . . . And I feel weak as I try to convey some slight impression of Jaynes' fantastic vision in this short review. Not since Freud and Jung has anyone had the daring and background to pull together such a far reaching theory." − Ernest Rossi, Ph.D., Professor of Neuroscience, in Psychological Perspectives
"... Scientific interest in [Jaynes's] work has been re-awakened by the consistent findings of right-sided activation patterns in the brain, as retrieved with the aid of neuroimaging studies in individuals with verbal auditory hallucinations." − Jan Dirk Blom, M.D, Ph.D., in A Dictionary of Hallucinations
"One's first inclination is to reject all of it out of hand as science fiction, imaginative speculation with no hard evidence; but, curiously, if one is patient and hears out the story (Jaynes's style is irresistible) the arguments are not only entertaining but persuasive." − George Adelman, Department of Brain & Cognitive Sciences, MIT, in Library Journal
"Genes affecting personality, reproductive strategies, cognition, are all able to change significantly over few-millennia time scales if the environment favors such change — and this includes the new environments we have made for ourselves, things like new ways of making a living and new social structures. ... There is evidence that such change has occurred. ... On first reading, Breakdown seemed one of the craziest books ever written, but Jaynes may have been on to something." − Gregory Cochran, Ph.D., Adjunct Professor of Anthropology at the University of Utah
"He is as startling as Freud was in The Interpretation of Dreams, and Jaynes is equally adept at forcing a new view of known human behavior." − Raymond Headlee, in American Journal of Psychiatry
"[Jaynes's] description of this new consciousness is one of the best I have come across." − Morris Berman, Ph.D., in Wandering God: A Study in Nomadic Spirituality
I was fascinated some years back when I encountered the phenomanon of right and left brain. Then I had a boss with a brilliant left brain and a thoroughly fxxxed up right brain. I spent 3 years pulling him out of stupid messes that his right brain kept getting him into. On the other hand we accomplished some good things with his left brain (and mine). ;-)