This book is the only one Jaynes (1920 - 1997) ever published. Although he is widely considered a kook, serious authors do quote those of his ideas that corroborate their views.

Jaynes’ basic tenet is described in several reviews on the internet, such as by Amazon, Wikipedia, Psych Central, The Imaginatorium, and Desmond Meraz. There is also a Julian Jaynes Society where you can hear a brief but good quality excerpt from one of his lectures. 

I will try to not repeat the information which is already available in other reviews, but rather focus on two of the many sub-themes running through Jaynes’s book. The first I choose because I profoundly agree with it, the second because I profoundly disagree.

What is consciousness, alias the mind, soul, psyche, personality, or inner world? Jaynes does what so may other authors fail to do, namely thoroughly discusses what he means when he uses these terms. But the most insightful question he asks – and answers – is: Where is consciousness?

Most people would answer: “Between the ears.” This, Jaynes shows us, is precisely where it is not. Using examples from ancient Greek literature, Jaynes demonstrates that millennia ago people associated their thoughts and feelings with just about every body part except their heads. Examples are:

• Lungs (one holds his breath in anticipation, or breathes heavily with excitement)
• Heart (pounds, or skips a beat)
• Stomach (a sinking feeling)
• Knees (weak, turn to water)
• Hands (tremble)
  

I'm sure we could all think of more examples from our own consciousness, such as:

• Skin (goose bumps)
• Throat (lump)
• Spine (chills)
• Cheeks (blushing)

None of the body parts that signal our consciousness to us occupies the space where we know our brain to be, except perhaps when we have a literal headache. Since Jaynes wrote this book, psychoneurologists have acquired newfangled scans, which they claim light up when areas of the brain are used. I personally have no more faith in these claims than I have in the animal research referred to below.

So where is consciousness? Jaynes states: nowhere. This doesn’t mean that our thoughts and feelings aren’t real. It means that they don’t exist in space. In fact, he continues, it is not possible to describe them except by metaphors. He comes just short of acknowledging that they do not belong to the material world. Unfortunately, he does not arrive at the obvious conclusion: that therefore they are unobservable, and thus fall outside the realm of valid subject matter for scientific research. Instead he asserts that (somatic) medicine leans heavily on the use of metaphor as well.

So much for what Jaynes and I agree on, and now for the disagreement. Jaynes claims that stress is decision-making. This is not a shorthand way of saying that the necessity or pressure to make a decision causes stress. Jaynes isn’t given to shorthand, and anyway, he states explicitly, “It has now been established that decision-making … is precisely what stress is.” (page 93). He mentions no other explanation for stress. Our politicians, who suggest that citizens would be much happier if the government limited their choices by curtailing their freedoms, would surely be delighted with this support from Jaynes.

How has the stress=decision-making equation been established, according to Jaynes? By experiments on rats and monkeys. The animals supposedly developed stomach ulcers when placed in conditions that compelled them to make decisions. However, what these experiments really prove is that “scientific research” sets out to justify the researchers’ beliefs, whatever they are. In those days, it was believed that stomach ulcers are caused by stress. Nowadays we know they are caused by a bacterium called heliobacter pylori. Although I don’t doubt that the unfortunate animals in the experiments were highly stressed, the researchers were probably lying about the ulcers they claimed to find in their stomachs. I trust they were telling the complete truth about how they tortured them.

If not decision-making, then what causes stress? In my opinion, it is powerlessness. The importance of the distinction is illustrated by the political implications, not to mention the "therapeutic" ones.

Besides these two sub-themes, a few more points in Jayne’s argument warrant attention.

He is to be commended for daring to tackle the sensitive issue of the origin of religion, so ubiquitous in human society. As an evolutionist, he contends that at one point in man’s development religion favored natural selection. How? It made decision-making possible. And that was necessary for the development of agriculture. Without agriculture, man might not have survived.

He places the origin of religion in speech. Speech itself, according to him, evolved when man’s migration northwards necessitated a means of communicating in the dark. But why would pre-man, being diurnal whether north or south, need to communicate in the dark, and why would speech be an adaptive way to do it? Furthermore, those equatorial societies which apparently according to Jaynes didn't need to communicate in the dark, and also never developed agriculture, nevertheless developed speech, religion, consciousness, and the whole kit and kaboodle. Jaynes might have come up with a more plausible theory if he had read Elaine Morgan's 1972 bestseller, The Descent of Woman.

If I may speak my mind, bicameral or not, in admittedly trite metaphors for a moment, then I would sum up Jaynes’s book as lots of food for thought, but also lots of empty calories.