Le métier d’homme est difficile.
—Georges Simenon, Le neige était sale

In his memoirs, Sir Arthur Conan Doyle says that the philosophy of Moleschott was all the rage when he was a medical student in Edinburgh during the late 1870s and early 1880s. Jacob Moleschott (1822–93) was a Dutch physiologist who had also studied philosophy in his youth and was a militant materialist. He is remembered today, if at all, for a couple of aphorisms that sum up his philosophy: “There is no thought without phosphorus” and “The brain secretes thought as the liver secretes bile.”

I suppose it is true that, metaphorically speaking, thought can become as blocked as bile, and even more irritant in its effects. But this summary, and surely very premature, dismissal of the puzzle of human consciousness and all its associated problems did not long satisfy Conan Doyle, who perhaps went to the other extreme and came to believe in everything from spirit messages to ectoplasm and fairies at the bottom of the garden. Overall, it is not easy to say which of the pair was the more irrational, Conan Doyle or Moleschott, though it is easy to say which was the more attractive. If I had to choose, however, I should award the palm for irrationality to Moleschott because he was so unconsciously prey to the sin of pride, believing himself to have fathomed the unfathomable (give or take an experiment or two).

Of course, Moleschott was neither the