In Book ii., where we discussed the method of Egoistic Hedonism, we did not take occasion to examine any proof of its first principle: and in the case of Universalistic Hedonism also, what primarily concerns us is not how its principle is to be proved to those who do not accept it, but what consequences are logically involved in its acceptance. At the same time it is important to observe that the principle of aiming at universal happiness is more generally felt to require some proof, or at least (as Mill puts it) some ``considerations determining the mind to accept it'', than the principle of aiming at one's own happiness. From the point of view, indeed, of abstract philosophy, I do not see why the Egoistic principle should pass unchallenged any 'more than the Universalistic. I do not see-why the axiom of Prudence should not be questioned, when it conflicts with present inclination, on a ground similar to that on which Egoists refuse to admit the axiom of Rational Benevolence. If the Utilitarian has to answer the question, `Why should I sacrifice my own happiness for the greater happiness of another?' it must surely be admissible to ask the Egoist, `Why should I sacrifice a present pleasure for a greater one in the future? Why should I concern myself about my own future feelings any more than about the feelings of other persons?' It undoubtedly seems to Common Sense paradoxical to ask for a reason why one should seek one's own happiness oil the whole; but I do not see how the demand can be repudiated as absurd by those who adopt the views of the extreme empirical school of psychologists, although those views are commonly supposed to have a close affinity with Egoistic Hedonism. Grant that the Ego is merely a system. of coherent phenomena, that the permanent identical `I' is not a fact but a fiction, as Hume and his followers maintain; why, then, should one part of the series of feelings into which the Ego is resolved be concerned with another part of the same series, any more than with any other series?
However, I will not press this question now; since I admit that Common Sense does not think it worth while to supply the individual with reasons for seeking his own interest. Reasons for doing his duty---according to the commonly accepted standard of duty---are not held to be equally superfluous: indeed we find that utilitarian reasons are continually given for one or other of the commonly received rules of morality. Still the fact that certain rules are commonly received as binding, though it does not establish their self-evidence, renders it generally unnecessary to prove their authority to the Common Sense that receives them: while for the same reason a Utilitarian who claims to supersede them by a higher principle is naturally challenged, by Intuitionists no less than by Egoists, to demonstrate the legitimacy of his claim. To this challenge some Utilitarians would reply by saying that it is impossible to ``prove'' a first principle and this is of course true, if by proof we mean a process which exhibits the principle in question as an inference from premises upon which it remains dependent for its certainty; for these premises, and not the inference drawn from them, would then be the real first principles. Nay, if Utilitarianism is to be proved to a man who already holds some other moral principles,---whether he be an Intuitional moralist, who regards as final the principles of Truth, Justice, Obedience to authority, Purity, etc., or an Egoist who regards his own interest as the ultimately reasonable end of his conduct,---it would seem that the process must be one which establishes a conclusion actually superior in validity to the premises from which it starts. For the Utilitarian prescriptions of duty are prima facie in conflict, at certain points and under certain circumstances, both with rules which the Intuitionist regards as self-evident, and with the dictates of Rational Egoism; so that Utilitarianism, if accepted at all, must be accepted as overruling Intuitionism and Egoism. At the same time, if the other principles are not throughout taken as valid, the so-called proof does not seem to be addressed to the Intuitionist or Egoist at all. How shall we deal with this dilemma? How is such a process---clearly different from ordinary proof---possible or conceivable? Yet there certainly seems to be a general demand for it. Perhaps we may say that what is needed is a line of argument which on the one hand allows the validity, to a certain extent, of the maxims already accepted, and on the other hand shows them to be not absolutely valid, but needing to be controlled and completed by some more comprehensive principle.
Such a line of argument, addressed to Egoism, was given in chap. xiii. of the foregoing book. It should be observed that the applicability of this argument depends on the manner in which the Egoistic first principle is formulated. If the Egoist strictly confines himself to stating his conviction that he ought to take his own happiness or pleasure as his ultimate end, there seems no opening for any line of reasoning to lead him to Universalistic Hedonism as a first principle; it cannot be proved that the difference between his own happiness and another's happiness is not for him all-important. In this case all that the Utilitarian can do is to effect as far as possible a reconciliation between the two principles, by expounding to the Egoist the sanctions of rules deduced from the Universalistic principle,---i.e. by pointing out the pleasures and pains that may be expected to accrue to the Egoist himself from the observation and violation respectively of such rules. It is obvious that such an exposition has no tendency to make him accept the greatest happiness of the greatest number as his ultimate end; but only as a means to the end of his own happiness. It is therefore totally different from a proof (as above explained) of Universalistic Hedonism. When, however, the Egoist puts forward, implicitly or explicitly, the proposition that his happiness or pleasure is Good, not only for him but from the point of view of the Universe,---as (e.g.) by saying that `nature designed him to seek his own happiness,'---it then becomes relevant to point out to him that his happiness cannot be a more important part of Good, taken universally, than the equal happiness of any other person. And thus, starting with his own principle, he may be brought to accept Universal happiness or pleasure as that which is absolutely and without qualification Good or Desirable: as an end, therefore, to which the action of a reasonable agent as such ought to be directed.
This, it will be remembered, is the reasoning that I used in chap. xiii. of the preceding book in exhibiting the principle of Rational Benevolence as one of the few Intuitions which stand the test of rigorous criticism. It should be observed, however, that as addressed to the Intuitionist, this reasoning only shows the Utilitarian first principle to be one moral axiom: it does not prove that it is sole or supreme. The premises with which the Intuitionist starts commonly include other formulae held as independent and self-evident. Utilitarianism has therefore to exhibit itself in the twofold relation above described, at once negative and positive, to these formulae. The Utilitarian must, in the first place, endeavour to show to the Intuitionist that the principles of Truth, Justice, etc. have only a dependent and subordinate validity: arguing either that the principle is really only affirmed by Common Sense as a general rule admitting of exceptions and qualifications, as in the case of Truth, and that we require some further principle for systematising these exceptions and qualifications; or that the fundamental notion is vague and needs further determination, as in the case of Justice; and further, that the different rules are liable to conflict with each other, and that we require some higher principle to decide the issue thus raised; and again, that the rules are differently formulated by different persons, and that these differences admit of no Intuitional solution, while they show the vagueness and ambiguity of the common moral notions to which the Intuitionist appeals.
This part of the argument I have perhaps sufficiently developed in the preceding book. It remains to supplement this line of reasoning by developing the positive relation that exists between Utilitarianism and the Morality of Common Sense: by showing how Utilitarianism sustains the general validity of the current moral judgments, and thus supplements the defects which reflection finds in the intuitive recognition of their stringency; and at the same time affords a principle of synthesis, and a method for binding the unconnected and occasionally conflicting principles of common moral reasoning into a complete and harmonious system. If systematic reflection upon the morality of Common Sense thus exhibits the Utilitarian principle as that to which Common Sense naturally appeals for that further development of its system which this same reflection shows to be necessary, the proof of Utilitarianism seems as complete as it can be made. And since, further---apart from the question of proof---it is important in considering the method of Utilitarianism to determine exactly its relation to the commonly received rules of morality, it will be proper to examine this relation at some length in the following chapter.