We are assured, that the human soul is a simple substance. It should then be the same in every individual, each having the same intellectual faculties; yet this is not the case. Men differ as much in the qualities of the mind, as in the features of the face. There are human beings as different from one another, as man is from a horse or a dog. What conformity or resemblance do we find between some men? What an infinite distance is there between the genius of a Locke or a Newton, and that of a peasant, Hottentot, or Laplander?

Man differs from other animals only in his organization, which enables him to produce effects, of which animals are not capable. The variety, observable in the organs of individuals of the human species suffices to explain the differences in what is called their intellectual faculties. More or less delicacy in these organs, warmth in the blood, mobility in the fluids, flexibility or stiffness in the fibres and nerves, must necessarily produce the infinite diversity, which we observe in the minds of men. It is by exercise, habit and education, that the mind is unfolded and becomes superior to that of others. Man, without culture and experience, is as void of reason and industry, as the brute. A stupid man is one, whose organs move with difficulty, whose brain does not easily vibrate, whose blood circulates slowly. A man of genius is he, whose organs are flexible, whose sensations are quick, whose brain vibrates with celerity. A learned man is he, whose organs and brain have been long exercised upon objects to which he is devoted.

Without culture, experience, or reason, is not man more contemptible and worthy of hatred, than the vilest insects or most ferocious beasts? Is there in nature a more detestable being, than a Tiberius, a Nero, or a Caligula? Have those destroyers of the human race, known by the name of conquerors, more estimable souls than bears, lions, or panthers? Are there animals in the world more detestable than tyrants?