Philosophers and psychiatrists should explain why it is that we mathematicians are in the habit of systematically erasing our footsteps. Scientists have always looked askance at this strange habit of mathematicians, which has changed little from Pythagoras to our day.
If the spirit has passed through a great many sensations, possibly it can no longer be sated with them, but grows more excited, and demands more sensations, and stronger and stronger ones, until at length it falls exhausted.