It remains to ask how far a scientific investigation of the causes of pleasure and pain can assist us in dealing with this practical problem. Now it is obvious that for deciding which of two courses of action is preferable on hedonistic grounds, we require not only to measure pains and pleasures of different kinds, but also to ascertain how they may be produced or averted. In most important prudential decisions, complex chains of consequences are foreseen as intervening between the volition we are immediately to initiate and the feelings which constitute the ultimate end of our efforts; and the degree of accuracy with which we forecast each link of these chains obviously depends upon our knowledge, implicit or explicit, of the relations of cause and effect among various natural phenomena. But if we suppose the different elements and immediate sources of happiness to have been duly ascertained and valued, the investigation of the conditions of production of each hardly belongs to a general treatise on the method of ethics; but rather to some one or other of the special arts subordinate to the general art of conduct. Of these subordinate arts some have a more or less scientific basis, while others are in a merely empirical stage; thus if we have decided how far health is to be sought, it belongs to the systematic art of hygiene, based on physiological science, to furnish a detailed plan of seeking it; so far, on the other hand, as we aim at power or wealth or domestic happiness, such instruction as the experience of others can give will be chiefly obtained in an unsystematic form, either from advice relative to our own special circumstances, or from accounts of success and failure in analogous situations. In either case the exposition of such special arts does not appear to come within the scope of the present treatise; nor could it help us in dealing with the difficulties of measuring pleasures and pains which we have considered in the previous chapters. It may, however, be thought that a knowledge of the causes of pleasure and pain may carry us beyond the determination of the means of gaining particular kinds of pleasure and avoiding particular kinds of pain; and enable us to substitute some deductive method of evaluing the elements of happiness for the empirical-reflective method of which we have seen the defects.[132]