How do you react when you come across a bear in the woods? William James begins his essay of 1884 on human emotion with the commonsense view: “we meet a bear, are frightened and run”. Wrong, says James. “This order of sequence is incorrect.” It is not that we run because we are frightened. It is that we find ourselves running and then, on experiencing this bodily reaction, call it fear. Reversal of an assumed arrow of causation is a hallmark of many conceptual breakthroughs, especially in domains where the truth is counterintuitive, or where it supports a narrative we don’t like. As with Galileo, a conceptual reversal may seem heretical at first, but in time we may see that it explains things that once made no sense.
