Human reason has this peculiar fate,” Immanuel Kant wrote in 1781, “that in one species of its knowledge it is burdened by questions which, as prescribed by the very nature of reason itself, it is not able to ignore, but which, as transcending all its powers, it is also not able to answer.” He was talking about the way reason can speculate about, and yet not know, the ideas that transcend it. For some philosophers, consciousness—what Kant called the self—counts as one of these ideas. We can no more illuminate the nature of our selfhood than, as in a celebrated metaphor sketched by Julian Jaynes,