When I speak of knowledge as an ingredient of the good life, I am not thinking of ethical knowledge, but of scientific knowledge and knowledge of particular facts. I do not think there is, strictly speaking, such a thing as ethical knowledge. If we desire to achieve some end, knowledge may show us the means, and this knowledge may loosely pass as ethical. But I do not believe that we can decide what sort of conduct is right or wrong except by reference to its probable consequences. Given an end to be achieved, it is a question for science to discover how to achieve it. All moral rules must be tested by examining whether they tend to realize ends that we desire. I say ends that we desire, not ends that we _ought_ to desire. What we “ought” to desire is merely what someone else wishes us to desire. Usually it is what the authorities wish us to desire――parents, schoolmasters, policemen, and judges. If you say to me “you ought to do so-and-so,” the motive power of your remark lies in my desire for your approval――together, possibly, with rewards or punishments attached to your approval or disapproval. Since all behaviour springs from desire, it is clear that ethical notions can have no importance except as they influenced desire. They do this through the desire for approval and the fear of disapproval. These are powerful social forces, and we shall naturally endeavour to win them to our side if we wish to realize any social purpose. When I say that the morality of conduct is to be judged by its probable consequences, I mean that I desire to see approval given to behaviour likely to realize social purposes which we desire, and disapproval to opposite behaviour. At present this is not done; there are certain traditional rules according to which approval and disapproval are meted out quite regardless of consequences. But this is a topic with which we shall deal in the next chapter.