The reason we don’t always behave in a way which corresponds with conventional ideas of rationality is not because we are silly: it is because we know more than we know we know. I did not decide to travel to the airport by back roads because I had calculated the level of variance in journey time – I did it instinctively, and was only aware of my unconscious reasoning in retrospect. ‘The heart has reasons of which reason knows nothing,’ as Pascal put it.*
