Questions about ends, he says (pp. 52-3), are, in other words, questions about what things are desirable. The utilitarian doctrine is, that happiness is desirable, and the only thing desirable, as an end; all other things being only desirable as means to that end. What ought to be required of this doctrine—what conditions is it requisite that the doctrine should fulfil—to make good its claim to be believed? (§ 40 ¶ 1)

The only proof capable of being given that a thing is visible, is that people actually see it. The only proof that a sound is audible, is that people hear it; and so of the other sources of our experience. In like manner, I apprehend, the sole evidence it is possible to produce that anything is desirable, is that people do actually desire it. If the end which the utilitarian doctrine proposes to itself were not, in theory and in practice, acknowledged to be an end, nothing could ever convince any person that it was so. 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 the 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 all persons. Happiness has made out its title as one of the ends of conduct, and consequently one of the criteria of morality. (§ 40 ¶ 2)

There, that is enough. That is my first point. Mill has made as naïve and artless a use of the naturalistic fallacy as anybody could desire. Good, he tells us, means desirable, and you can only find out what is desirable by seeking to find out what is actually desired. This is, of course, only one step towards the proof of Hedonism; for it may be, as Mill goes on to say, that other things beside pleasure are desired. Whether or not pleasure is the only thing desired is, as Mill himself admits (p. 58), a psychological question, to which we shall presently proceed. The important step for Ethics is this one just taken, the step which pretends to prove that good means desired. (§ 40 ¶ 3)

Well, the fallacy in this step is so obvious, that it is quite wonderful how Mill failed to see it. The fact is that desirable does not mean able to be desired as visible means able to be seen. The desirable means simply what ought to be desired or deserves to be desired; just as the detestable means not what can be but what ought to be detested and the damnable what deserves to be damned. Mill has, then, smuggled in, under cover of the word desirable, the very notion about which he ought to be quite clear. Desirable does indeed mean what it is good to desire; but when this is understood, it is no longer plausible to say that our only test of that, is what is actually desired. Is it merely a tautology when the Prayer Book talks of good desires? Are not bad desires also possible? Nay, we find Mill himself talking of a better and nobler object of desire (p. 10), as if, after all, what is desired were not ipso facto good, and good in proportion to the amount it is desired. Moreover, if the desired is ipso facto the good; then the good is ipso facto the motive of our actions, and there can be no question of finding motives for doing it, as Mill is at such pains to do. If Mill’s explanation of desirable be true, then his statement (p. 26) that the rule of action may be confounded with the motive of it is untrue; for the motive of action will then be according to him ipso facto its rule; there can be no distinction between the two, and therefore no confusion, and thus he has contradicted himself flatly. These are specimens of the contradictions, which, as I have tried to shew, must always follow from the use of the naturalistic fallacy; and I hope I need now say no more about the matter. (§ 40 ¶ 4)