The revolutionary demand for equality was, historically speaking, a protest against arbitrary inequality. It was a protest against the existence of privileges accompanied by no duties. When the rich man could only answer the question, "What have you done to justify your position?" by the famous phrase of Beaumarchais, "I took the trouble to be born," he was obviously in a false position. The demand for a society founded upon reason, in this sense that a sufficient reason should be given for all differences, was, it seems to me, perfectly right; and, moreover, was enough to condemn the then established system. But when this demand has been so constructed as to twist a logical rule, applicable to all scientific reasoning, into a dogmatic assertion that certain concrete beings were in fact equal, and to infer that they should have equal rights, it ceased to be logical at all, and has been a fruitful parent of many fallacies. Reasonable beings require a sufficient reason for all differences of conduct, for the difference between their treatment of a man and a monkey or a white man and a black, as well as for differences between treatment of rich and poor or wise men and fools; and there must, as the same principle implies, be also a sufficient reason for treating all members of a given class equally. We have to consider whether, for any given purpose, the differences between human beings and animals, Englishmen and negroes, men and women, are or are not of importance for our purpose. When the differences are irrelevant we neglect them or admit the claim to equality of treatment. But the question as to relevance is not to be taken for granted either way. It would be a very convenient but a very unjustifiable assumption in many cases, as it might save an astronomer trouble if he assumed that every star was equal to every other star.