gression. In fact, moral progress implies a growing repugnance to the infliction of pain, and depends partially upon sympathy. Its causes, then, are not merely physiological. It is influenced by the psychological principle, that the repugnance to the infliction of pain diminishes according as the infliction satisfies a want stronger than the mental representation of the pain inflicted. When we consider the increasing importance of property with advancing civilization, this principle explains the greater severity with which crimes against property are punished in the countries of more complex social development. It explains, also, the growing harshness of Hellenic slavery after advancing culture had multiplied the wants of the masters. Another cause influencing moral progress is the fact that the intensity of sympathy varies with resemblance. This explains many historic transformations of the moral sense, especially those which involve the relations of social classes. A more complex psychological process often modifying moral advancement, is the law of comparison. If two institutions are to serve the same end, we regard as immoral the one which costs more pain. Thus we come to regard with horror the methods of mediaeval surgery, slavery, and child-labor—always by comparison with a less oppressive system. An important result of this principle of comparison is the tendency of different moralities to an equilibrium. The less advanced morality tends to attain the degree of development of the more advanced. This effect is indirect. Moral theories supporting the objectionable institutions become hypocritical. Men seek for justifications of all kinds for a state of things which they know to be condemned by the consciences of others. The theory of moral progress here detailed rests upon simple psychological laws, rather than upon biological transformations. The contradictions of human morality are explained by the fact that the psychological principles involved are many, and act sometimes together, sometimes in opposition.
The power to distinguish between good and evil makes man a moral being. What is the principle of distinction, and how are we led to regard the moral law as the highest law of our will? Good and evil, falsehood and truth, are confused in the world. We must either assert a likeness in their nature and origin, or deny it. If we do the
