§5. 1 must now point out---if it has not long been apparent to the reader---that the self-evident principles laid down in § 3 do not specially belong to Intuitionism in the, restricted sense which, for clear distinction of methods, I gave to this term at the outset of our investigation. The axiom of Prudence, as I have given it, is a self-evident principle, implied in Rational Egoism as commonly accepted. Again, the axiom of Justice or Equity as above stated---`that similar cases ought to be treated similarly'---belongs in all its applications to Utilitarianism as much as to any system commonly called Intuitional: while the axiom of Rational Benevolence is, in my view, required as a rational basis for the Utilitarian system.
Accordingly, I find that I arrive, in my search for really clear and certain ethical intuitions, at the fundamental principle of Utilitarianism. I must, however, admit that the thinkers who in recent times have taught this latter system, have not, for the most part, expressly tried to exhibit the truth of their first principle by means of any such procedure as that above given. Still, when I examine the ``proof'' of the ``principle of Utility'' presented by the most persuasive and probably the most influential among English expositors of Utilitarianism,---J. S. Mill,---I find the need of some such procedure to complete the argument very plain and palpable.
Mill begins by explaining that though ``questions of ultimate ends are not amenable'' to ``proof in the ordinary and popular meaning of the term'', there is a ``larger meaning of the word proof'' in which they are amenable to it. ``The subject'', he says, is ``within the cognisance of the rational faculty … Considerations may be presented capable of determining the intellect to ``accept'' the Utilitarian formula. He subsequently makes clear that by ``acceptance of the Utilitarian formula'' he means the acceptance, not of the agent's own greatest happiness, but of ``the greatest amount of happiness altogether'' as the ultimate ``end of human action'' and ``standard of morality'': to promote which is, in the Utilitarian view, the supreme ``directive rule of human conduct''. Then when he comes to give the ``proof''---in the larger sense before explained---of this rule or formula, he offers the following argument. ``The sole evidence it is possible to produce that any thing is desirable, is that people do actually desire it … No reason can be given why the general happiness is desirable, except that each person, so far as he believes it to be attainable, desires his own happiness. This, however, being a fact, we have not only all the proof which the case admits of, but all which it is possible to require, that happiness is a good: that each person's happiness is a good to that person, and the general happiness, therefore, a good to the aggregate of persons.'' [2] He then goes on to argue that pleasure, and pleasure alone, is what all men actually do desire.
Now, as we have seen, it is as a ``standard of right and wrong'', or ``directive rule of conduct'', that the utilitarian principle is put forward by Mill: hence, in giving as a statement of this principle that ``the general happiness is desirable'', he must be understood to mean (and his whole treatise shows that he does mean) that it is what each individual ought to desire, or at least---in the stricter sense of `ought'---to aim at realising in action. But this proposition is not established by Mill's reasoning, even if we grant that what is actually desired may be legitimately inferred to be in this sense desirable. For an aggregate of actual desires, each directed towards a different part of the general happiness, does not constitute an actual desire for the general happiness, existing in any individual; and Mill would certainly not contend that a desire which does not exist in any individual can possibly exist in an aggregate of individuals. There being therefore no actual desire---so far as this reasoning goes---for the general happiness, the proposition that the general happiness is desirable cannot be in this way established: so that there is a gap in the expressed argument, which can, I think, only be filled by some such proposition as that which I have above tried to exhibit as the intuition of Rational Benevolence.
Utilitarianism is thus presented as the final form into which Intuitionism tends to pass, when the demand for really self-evident first principles is rigorously pressed. In order, however, to make this transition logically complete, we require to interpret `Universal Good' as `Universal Happiness'. And this interpretation cannot, in my view, be justified by arguing, as Mill does, from the psychological fact that Happiness is the sole object of men's actual desires, to the ethical conclusion that it alone is desirable or good; because in Book i. chap. iv. of this treatise I have attempted to show that Happiness or Pleasure is not the only object that each for himself actually desires. The identification of Ultimate Good with Happiness is properly to be reached, I think, by a more indirect mode of reasoning; which I will endeavour to explain in the next Chapter. {Note.}