The metaphor is based on the idea of lateralization of brain function although each half of a normal human brain is constantly communicating with the other through the corpus callosum. The metaphor is not meant to imply that the two halves of the bicameral brain were “cut off” from each other but that the bicameral mind was experienced as a different, non-conscious mental schema wherein volition in the face of novel stimuli was mediated through a linguistic control mechanism and experienced as auditory verbal hallucination.

Bicameral mentality would be non-conscious in its inability to reason and articulate about mental contents through meta-reflection, reacting without explicitly realizing and without the meta-reflective ability to give an account of why one did so. The bicameral mind would thus lack metaconsciousness, autobiographical memory, and the capacity for executive “ego functions” such as deliberate mind-wandering and conscious introspection of mental content. When bicamerality as a method of social control was no longer adaptive in complex civilizations, this mental model was replaced by the conscious mode of thought which, Jaynes argued, is grounded in the acquisition of metaphorical language learned by exposure to narrative practice.
According to Jaynes, ancient people in the bicameral state of mind would have experienced the world in a manner that has some similarities to that of a person with schizophrenia. Rather than making conscious evaluations in novel or unexpected situations, the person would hallucinate a voice or “god” giving admonitory advice or commands and obey without question: One would not be at all conscious of one’s own thought processes per se. Jaynes’s hypothesis is offered as a possible explanation of “command hallucinations” that often direct the behavior of those afflicted by first rank symptoms of schizophrenia, as well as other voice hearers.
Jaynes’s Evidence
Jaynes built a case for this hypothesis that human brains existed in a bicameral state until as recently as 3,000 years ago by citing evidence from many diverse sources including historical literature. He took an interdisciplinary approach, drawing data from many different fields.[3] Jaynes asserted that, until roughly the times written about in Homer’s Iliad, humans did not generally have the self-awareness characteristic of consciousness as most people experience it today. Rather, the bicameral individual was guided by mental commands believed to be issued by external “gods”—commands which were recorded in ancient myths, legends and historical accounts. This is exemplified not only in the commands given to characters in ancient epics but also the very muses of Greek mythology which “sang” the poems. According to Jaynes, the ancients literally heard muses as the direct source of their music and poetry.
Jaynes asserts that in the Iliad and sections of the Old Testament no mention is made of any kind of cognitive processes such as introspection, and there is no apparent indication that the writers were self-aware. Jaynes suggests, the older portions of the Old Testament (such as the Book of Amos) have few or none of the features of some later books of the Old Testament (such as Ecclesiastes) as well as later works such as Homer’s Odyssey, which show indications of a profoundly different kind of mentality—an early form of consciousness.
In ancient times, Jaynes noted, gods were generally much more numerous and much more anthropomorphic than in modern times, and speculates that this was because each bicameral person had their own “god” who reflected their own desires and experiences.
He also noted that in ancient societies the corpses of the dead were often treated as though still alive (being seated, dressed, and even fed) as a form of ancestor worship, and Jaynes argued that the dead bodies were presumed to be still living and the source of auditory hallucinations.[3] This adaptation to the village communities of 100 individuals or more formed the core of religion. Unlike today’s hallucinations, the voices of ancient times were structured by cultural norms to produce a seamlessly functioning society.
Jaynes inferred that these “voices” came from the right brain counterparts of the left brain language centres; specifically, the counterparts to Wernicke’s area and Broca’s area. These regions are somewhat dormant in the right brains of most modern humans, but Jaynes noted that some studies show that auditory hallucinations correspond to increased activity in these areas of the brain.
Jaynes notes that even at the time of publication there is no consensus as to the cause or origins of schizophrenia. Jaynes argues that schizophrenia is a vestige of humanity’s earlier bicameral state. Recent evidence shows that many schizophrenics do not just hear random voices but experience “command hallucinations” instructing their behavior or urging them to commit certain acts.
As support for Jaynes’s argument, these command hallucinations are little different from the commands from gods which feature prominently in ancient stories. Indirect evidence supporting Jaynes’s theory that hallucinations once played an important role in human mentality can be found in the recent book Muses, Madmen, and Prophets: Rethinking the History, Science, and Meaning of Auditory Hallucination by Daniel Smith.
Breakdown of Bicameralism
Jaynes theorized that a shift from bicameralism marked the beginning of introspection and consciousness as we know it today. According to Jaynes, this bicameral mentality began malfunctioning or “breaking down” during the 2nd millennium BCE. He speculates that primitive ancient societies tended to collapse periodically: for example, Egypt’s Intermediate Periods, as well as the periodically vanishing cities of the Mayas, as changes in the environment strained the socio-cultural equilibria sustained by this bicameral mindset.
The Bronze age collapse of the 2nd millennium BCE led to mass migrations and created a rash of unexpected situations and stresses which required ancient minds to become more flexible and creative. Self-awareness, or consciousness, was the culturally evolved solution to this problem. This necessity of communicating commonly observed phenomena among individuals who shared no common language or cultural upbringing encouraged those communities to become self-aware to survive in a new environment. Thus consciousness, like bicamerality, emerged as a neurological adaptation to social complexity in a changing world.
Jaynes further argues that divination, prayer, and oracles arose during this breakdown period, in an attempt to summon instructions from the “gods” whose voices could no longer be heard. The consultation of special bicamerally operative individuals, or of divination by casting lots and so forth, was a response to this loss, a transitional era depicted, for example, in the book of 1 Samuel. It was also evidenced in children who could communicate with the gods, but as their neurology was set by language and society they gradually lost that ability. Those who continued prophesying, being bicameral according to Jaynes, could be killed. Leftovers of the bicameral mind today, according to Jaynes, include mental illnesses such as schizophrenia and the hallucinations present in patients with split brain syndrome.

Bicameralism Bibliography:

Antisemitism is the litmus for a society’s fitness to continue progressing (as opposed to devolving, ultimately dying), because Jews injected the genetic breakdown of the bicameral mind – killed the old God(s)
  • breakdown of the bicameral mind – the death of the old Gods – spread globally but because of the semitic origin, its proliferation carried with it a deep deep culture of resentment against the semitic people (or their proxy) because no bicameral culture (i.e. created and serving the divided brain – the Old Gods) wanted the updated culture yet found it undeniable.
  • For a while this monocameral brainculture was antithetical, genetically, so resistance was both because it ran contrary to local custom and also contrary to the brains running it and the systems rewarding bicameral brains (witch doctors, priest caste, oracles, holy men, right of kings, etc).
  • Bicameral versus united identity brain might still be in tension, for some, but natural selection is irresistable so the advantage of the united mind for dealing with new environments, new conditions (adaptation) is a decisive at times. The collapse of Bronze Age culture, almost at the same time, almost universally, because of shifting climate and migration conflicts upending long-standing proto-civilisations was a perfect storm for the bicameral ritualistic polytheistic societies to be beaten by the humans with united brains adapting faster, reacting more effectively, winning the Darwinian race into the Iron Age.
  • New culture – more complex culture – overbears nature, despite no doubt many brains retaining the old bicameral predisposition.
  • Who knows how deeply embedded nurture becomes in the very development of the brain from its zygote startpoint:
    • Maybe the predisposition remains to this day and it’s why some are prone to religious dogma?
    • Could it explain why some are natural leaders – by dint of natural indepedence of thinking, submission to authority (or ritual rule) an anathema – and some (more) seem to be natural followers, preferring the group to solo?
  • In any case, the genetic advantage of the united mind is the well-spring of civilisation. History demonstrates. Whether or not human history’s paradigm shift originates in the breakdown of the bicameral mind into a united independent self-determinism (in a single brain), the sudden acceleration of civilization from around 2000-1000 BC is fact.
    • Art and literature from before this shift has no self-reflection, no inner voice, no stream of consciousness. At all. There isn’t even allegory or metaphor.
    • Art and literature after the shift is Homer, Aeschylus, Ovid etc.
    • Polytheistic cultures like Ancient Greece suddenly evolved their patheon into complex metaphorical stories.
    • Maths and philosophy begins. Democracy is invented.
    • Even as religions adapted to cope with these changes: the Jewish oral tradition stories (from bicameral brains) become the Old Testament, the stories distilled into New Testament scripture (from unicameral brains?). The difference, to us, in modern times is stark. Almost like the people of the Old Testament are a different species.
  • But change is resisted by those who don’t want to change or can’t change or feel the change alien to their world. Even if the change is undeniable, even if the progress plain for all to see. Resistance overwhelmed morphs into resentment. Resentment at populationwide scale becomes prejudice: bigotry, racism, whatever.
  • This paradigm shift from bicameral mind to united autonomy brain – writ large across culture – was only 4000-5000 years ago. Evolution by natural selection works slowly, as beneficial mutations become universal and in an organism complex like homo sapiens passing on genes in natural selection by macroculture ecosystems, 5000 years is the blink of an eye.
  • Ancient Eygpt was bicameral. Judea, Ancient Greece, Roman Empire, Medieval Europe, Renaissance Old World/New World Reconnected, Age of Reason, Industrialization, 20th Century Globalization, and we’re at today. Culturally it’s less than ten evolutionary phases.
  • Today, as a monoculture, we’ve long forgotten the original breakdown of the old ways and the old Gods, but could there be a specieswide PTSD from the extrusion of such large swathes of humanity from comfort of bicameral subservience (albeit in one brain) to the metaphorical newborn vulnerability of existential culture of autonomous (solitary) mind.
  • And the Jews carry the stigma. Blame for this cataclysm of culture, however improved the end result, develops into complex cultural neurosis in the subconscious; heritable as prejudices, justified by “feeling right” because the breakdown isn’t universal or instant or unequivocal anyway.
  • Progress, evolution, civilisation, higher function, kindness, compassionate society:  these are traits of a good society. Today, with its origins in the impossibly complex history of the species, antisemitism has become an allegory for the corrosion of those positive traits. Antisemitic societies are degenerating back towards the beastly states of mind and primitive states of community. Ironically, this is an inverted untermensch i.e. the untermensch is defined as the degenerate foreign stranger whose influence will poison good society.
  • In a big picture sense this may have been true, thousands of years ago, when the Jews inserted the conditions for the breakdown of the bicameral mind cultures; except it’s an antidote not a poison.
  • Today, the Jews are still “natural” targets, even if in many multicultural societies, it’s no longer simply Jews themselves in the crosshairs but traits associated with Jewish-cultural influences that drive change like economics, science, art, literature, psychology, intellectualism – evolved thinking versus visceral reacting (in the moment).
  • Antisemitism versus philosemitism has therefore become a perennial litmus for the trajectory of a modern society. Is its momentum towards an elevating goodness or is the society degrading towards beastmode? Judge by the treatment of the Jews (and other minorities). Especially the Jews.
  • Because the Jews broke the mould and carry the intergenerational stigma of killing the old gods. Which they did. And maybe they also liberated homo sapiens from the bicameral mind that was a form of perpetual mental slavery. The cultures of the bicameral brain were stagnant and bleak. The cultures of the post-bicameral era are watching video footage from vehicles filming the red rocks of Mars.