A scientist writing around the turn of the century remarked that all of the past generations of men have lived and died in a world of illusion. The unconscious irony in his observation consists in the fact that this man assumed the progress of science to have been so great that a clear vision of the world without illusion was, by his own time, possible. It is needless to add that he wrote before Einstein ... at a time when Mendel was just about to be rediscovered, and before the advances in the study of radioactivity ...