Some notes from my LW meetup lecture on book of Julian Jaynes: The Origin of Consciousness in the Breakdown of the Bicameral Mind. Not sure if legible for someone who wasn't there. May serve as a motivation to read the book.

Human brain has two hemispheres, relatively loosely connected, each of them is relatively independent (look up experiments when one hemisphere was disabled by e.g. injecting amytal into neck artery). Both can listen and see, but only the dominant hemisphere can talk. The corresponding part of the non-dominant hemisphere, when stimulated by electric current, creates super-realistic auditory -- and sometimes even visual -- hallucinations, similar to schizophrenia.

What is the evolutionary purpose of having a schizophrenia center in the brain? (This is just a speculation, skip this paragraph if it annoys you.) Julian Jaynes supposes that something similar to today's schizophrenia was actually an evolutionary precedessor of consciousness. Hallucinating voices of their fellow apes allowed our ancestors to create tribes of larger sizes than other primates. Belief in afterlife emerged as a side effect of hallucinating voices of dead tribe members. Obeying dead tribe leaders became a basis of religion. The hallucinations of specific people later evolved into hallucinations of culturally shared gods.

When the society becomes so complex that mere knowledge of rules and pattern-matching is not sufficient to solve existing problems, people have to develop theory of mind instead (first the theory of other minds; later, applying it to themselves, the consciousness), which made them lose the ability to see gods. Jaynes believes the switch from interacting with gods to consciousness happened during the "fall of Atlantis", which was a series of vulcanic eruptions in the Mediterranean sea, dramatically changing life in all local civilizations except for Egypt. In the absence of gods, "religions/superstition as we know it today" emerged. People started praying to absent gods, and making rituals to appease them; they also invented various forms of divination. Even then, a high level of stress can invoke the hallucinations again. The threshold of stress required seems to be genetic. People who retained the ability to speak with gods were called prophets. They were often uneducated people.

Some evidence: In ancient Egypt seeing hallucinations of other people was perfectly normal; the hallucinations were called "ka". In Iliad, people interacted with gods all the time; pretty much all thinking was outsourced to gods. (The later Odyssey already depicts humans with modern psychology: they make decisions, invent tricks, lie.) The Oracle of Delphi used illiterate teenage girls from peasant families to channel the god Apollon.

The Old Testament (a collections of books written and edited in different eras) also reflects the process. At the beginning, humans regularly interacted with gods; the latest of them was Moses. Then the interaction with gods was limited to prophets; often uneducated people, sometimes prophesizing against their wills. Sometimes they were killed either because their prophecies failed, or for political reasons when they prophesized for the wrong god. Gradually they were eradicated.

Relevant Biblical quotes:

"The words of Amos, one of the shepherds of Tekoa — the vision he saw concerning Israel … He said: The Lord roars from Zion and thunders from Jerusalem … This is what the Lord says: … This is what the Lord says: … This is what the Lord says: …" (Amos) He speaks while hearing the hallucinations.

"Amos answered Amaziah, “I was neither a prophet nor the son of a prophet, but I was a shepherd, and I also took care of sycamore-fig trees. But the Lord took me from tending the flock and said to me, ‘Go, prophesy to my people Israel.’" (Amos 7:14-15) Prophet explains to a professional priest why such a nobody as him is speaking for the mighty God.

"But Moses said to God, “Who am I that I should go to Pharaoh and bring the Israelites out of Egypt?”" (Exodus 3:11) Moses tries to avoid the role of prophet, because he doesn't feel high-status.

"Alas, Sovereign Lord,” I said, “I do not know how to speak; I am too young." (Jeremiah 1:6) "You persuaded me, Lord, and I was persuaded; you overpowered me and prevailed. I am ridiculed all day long; everyone mocks me. Whenever I speak, I cry out proclaiming violence and destruction. So the word of the Lord has brought me insult and reproach all day long. But if I say, “I will not mention his word or speak anymore in his name,” his word is in my heart like a fire, a fire shut up in my bones. I am weary of holding it in; indeed, I cannot." (Jeremiah 20:7-9) Jeremiah also tries to avoid this role, but to no end. Hallucinations come involuntarily, and they require to be acted upon; resistance is futile.

Related interesting phenomenon is hypnosis. That's something that Vulcan rationalists try to avoid, because it works differently in different cultural settings and for different people, so it seems to avoid scientific approach. Jaynes's explanation is that the non-dominant hemisphere hears the hypnotist's voice and decides to obey (usually because the person believes that this is how hypnosis really works, hence the cultural dependence), overruling the dominant hemisphere. How is hypnosis different from voluntary compliance? People who try faking it by conscious compliance provide worse results. For example, if you convince someone in hypnosis that they are a chicken, they can spend fifteen minutes happily clucking, while a person who fakes being hypnotized will become visibly bored.

Here is something that wasn't mentioned in the book, but I think it fits the pattern: In Zen Buddhism, priests used paradoxical puzzles called "koans" to make students "enlightened", and to verify that they really are "enlightened". If Jaynes's theory is true, it could have been a historical tool to turn off the bicameral (hallucinatory, pattern-matching) thinking, and turn on the consciousness. In other words, if you are a modern human interested in Buddhism, studying koans is probably just a waste of time: the abilities they promise you already have; and no, they aren't supernatural. (Also many koans are based on puns in languages you don't know, so you actually can't solve them.)

This is just my speculation: This theory could explain why it is useful to debate your thoughts with other people (e.g. in therapy; most obviously Rogerian therapy), or to accompany your decisions with rituals, as opposed to just thinking rationally about them. It is how the dominant hemisphere explains its intentions to the non-dominant hemisphere, which in turn can later provide the necessary willpower. This could also provide a hint to why highly intelligent people suffer so often from akrasia.