Man is a rational animal—so at least I have been told. … Aristotle, so far as I know, was the first man to proclaim explicitly that man is a rational animal. His reason for this view was … that some people can do sums. … It is in virtue of the intellect that man is a rational animal. The intellect is shown in various ways, but most emphatically by mastery of arithmetic. The Greek system of numerals was very bad, so that the multiplication table was quite difficult, and complicated calculations could only be made by very clever people.

It is a curious and painful fact that almost all the completely futile treatments that have been believed in during the long history of medical folly have been such as caused acute suffering to the patient. When anesthetics were discovered, pious people considered them an attempt to evade the will of God. It was pointed out, however, that when God extracted Adam's rib He put him into a deep sleep. This proved that anesthetics are all right for men; women, however, ought to suffer, because of the curse of Eve.

To avoid the various foolish opinions to which mankind are prone, no superhuman genius is required. A few simple rules will keep you, not from all error, but from silly error.

If throughout your life you abstain from murder, theft, fornication, perjury, blasphemy, and disrespect toward your parents, church, and your king, you are conventionally held to deserve moral admiration even if you have never done a single kind, generous or useful action. This very inadequate notion of virtue is an outcome of taboo morality, and has done untold harm.

If an opinion contrary to your own makes you angry, that is a sign that you are subsciously aware of having no good reason for thinking as you do. [...] The most savage controversies are those about matters as to which there is no good evidence either way. Persecution is used in theology, not in arithmetic, because in arithmetic there is knowledge, but in theology there is only opinion. So whenever you find yourself getting angry about a difference of opinion, be on your guard; you will probably find, on examination, that your belief is going beyond what the evidence warrants.

Patriots always talk of dying for their country and never of killing for their country.

Much that passes as idealism is disguised hatred or disguised love of power.