We all experience thinking as voices in our heads. When asked why he stifled parliamentary politics, Bismarck said he had so many voices arguing in his head he did not need to hear any more.
But apparently many people experience such voices audibly. Some hear them as God's commands, often to perform very specific tasks. In The New York Times this week, T. M. Luhrmann, an anthropology professor at Stanford University, reports that among evangelical churchgoers he has studied, a fair number have reported God having spoken, audibly, to them. There are such comforting messages as: "I will always love you."
More demanding ones include "Go start a school". And "Vote for [George W.] Bush". The person replied that he didn't even like Bush. To which God said: "I didn't ask you to like him."
Are these people crazy? Perhaps they are mildly schizophrenic. But to claim they are crazy, you have to make a lot of assumptions about the nature of voices in our heads. An obvious one is that there is no God. Of course, those evangelicals make lots of assumptions too in thinking they were reporting their experiences accurately.
I find these questions fascinating because they were decisively tackled in the 1976 cult classic The Origin of Consciousness in the Breakdown of the Bicameral Mind, by the late US psychologist Julian Jaynes. In it, he makes the seemingly absurd claim that people had no inward or subjective experiences - what he calls "mind spaces" - until about 3,000 years ago. Before that, people assumed the inner voices they heard were from outside of them - from gods, spirits or ghosts. Virtually all the evidence from anthropology and early literature Jaynes marshalled has been challenged or discredited. But his central claim is still an unanswered challenge: there is no logical or empirical reason to think the voices in our heads must be ours. Only the most extraordinary - and mysterious - revolution in human consciousness made us take possession of our innermost thoughts.
What prompted Jaynes to develop his bizarre theory? Apparently an audible voice he heard that told him: "Include the knower in the known!" He later said: "It lugged me to my feet absurdly exclaiming 'Hello?'."