OF all animals, man is the most unpredictable. Toynbee notwithstanding, history makes an uncertain prophet: the same circumstances, involving different times and different men, can lead to war or peace, love or hate, fraternity or murder. The same hereditary material, pooled by the same man and woman in the act of reproduction, can produce children who do not much resemble either their parents or one another. Even identical twins, issuing from the same egg, can vary; for instance, they never possess identical fingerprints or dispositions.
Classifications may not exist in nature, but order does....