To what then is to be attributed this opinion which has been often entertained about the uncertainty of morals? Chiefly to this,--that philosophers have not always distinguished the theoretical and the casuistical uncertainty of morals from the practical certainty. There is an uncertainty about details,--whether, for example, under given circumstances such and such a moral principle is to be enforced, or whether in some cases there may not be a conflict of duties: these are the exceptions to the ordinary rules of morality, important, indeed, but not extending to the one thousandth or one ten-thousandth part of human actions. This is the domain of casuistry. Secondly, the aspects under which the most general principles of morals may be presented to us are many and various. The mind of man has been more than usually active in thinking about man. The conceptions of harmony, happiness, right, freedom, benevolence, self-love, have all of them seemed to some philosopher or other the truest and most comprehensive expression of morality. There is no difference, or at any rate no great difference, of opinion about the right and wrong of actions, but only about the general notion which furnishes the best explanation or gives the most comprehensive view of them. This, in the language of Kant, is the sphere of the metaphysic of ethics. But these two uncertainties at either end, en tois malista katholou and en tois kath ekasta, leave space enough for an intermediate principle which is practically certain. The rule of human life is not dependent on the theories of philosophers: we know what our duties are for the most part before we speculate about them. And the use of speculation is not to teach us what we already know, but to inspire in our minds an interest about morals in general, to strengthen our conception of the virtues by showing that they confirm one another, to prove to us, as Socrates would have said, that they are not many, but one. There is the same kind of pleasure and use in reducing morals, as in reducing physics, to a few very simple truths. And not unfrequently the more general principle may correct prejudices and misconceptions, and enable us to regard our fellow-men in a larger and more generous spirit.