Behavior: The Lost Voices of the Gods

Julian Jaynes was six years old and staring at a yellow forsythia bush when the problem first entered his mind: "I thought, 'How do I know that other people see the same yellow I see?' I had the idea that there was a space in everyone else's head that I couldn't get to. How did that space get there?"

Jaynes, 55, a research psychologist at Princeton, now knows that what he was trying to comprehend was consciousness—and how it arose from mere matter. Indeed, he thinks he finally has the answer: consciousness arose from...