The superfluity of theoretical ethics is obvious in simple cases. Suppose, for instance, that your child is ill. Love makes you wish to cure it, and science tells you how to do so. There is not an intermediate stage of ethical theory, where it is demonstrated that your child had better be cured. Your act springs directly from desire for an end, together with knowledge of means. This is equally true of all acts, whether good or bad. The ends differ, and the knowledge is more adequate in some cases than in others. But there is no conceivable way of making people do things they do not wish to do. What is possible is to alter their desires by a system of rewards and penalties, among which social approval and disapproval are not the least potent. The question for the legislative moralist is, therefore: How shall this system of rewards and punishments be arranged so as to secure the maximum of what is desired by the legislative authority? If I say that the legislative authority has bad desires, I mean merely that its desires conflict with those of some section of the community to which I belong. Outside human desires there is no moral standard. Thus, what distinguishes ethics from science is not any special kind of knowledge, but merely desire. The knowledge required in ethics is exactly like the knowledge elsewhere; what is peculiar is that certain ends are desired, and that right conduct is what conduces to them. Of course, if the definition of right conduct is to make a wide appeal, the ends must be such as large sections of mankind desire. If I defined right conduct as that which increases my own income, readers would disagree. The whole effectiveness of any ethical argument lies in its scientific part, i. e. in the proof that one kind of conduct, rather than some other, is a means to an end which is widely desired. I distinguish, however, between ethical argument and ethical education. The latter consists in strengthening certain desires and weakening others. This is quite a different process, which will be separately discussed at a later stage. We can now explain more exactly the purport of the definition of the good life with which this chapter began. When I said that the good life consists of love guided by knowledge, the desire which prompted me was the desire to live such a life as far as possible, and to see others living it; and the logical content of the statement is that, in a community where men live in this way, more desires will be satisfied than in one where there is less love or less knowledge. I do not mean that such a life is “virtuous” or that its opposite is “sinful,” for these are conceptions which seem to me to have no scientific justification. CHAPTER III MORAL RULES