The trouble with philosophy, Amos thought, was that it didn’t play by the rules of science. The philosopher tested his theories of human nature on a sample size of one—himself. Psychology at least pretended to be a science. It kept at least one hand at all times on hard data. A psychologist might test whatever theory he devised on a representative sample of humanity. His theories might be tested by others, and his findings reproduced, or falsified. If a psychologist stumbled upon a truth he might make it stick.