In the seventeenth century the dualist philosopher Descartes, who argued that mind and brain are entirely separate entities, placed the human soul in the pineal gland. It was here, he said, that the material brain in some magical and mysterious way communicates with the mind and with the immaterial soul. I don’t know what he would have said if he could have seen my patients looking at their own brains on a video monitor, as some of them do when I operate under local anaesthetic.
