It is sometimes said that we live in an age that rejects authority. The statement, thus qualified, seems misleading; probably there never was a time … - Henry Sidgwick

We have next to consider who the “all” are, whose happiness is to be taken into account. Are we to extend our concern to all the beings capable of pleasure and pain whose feelings are affected by our conduct? or are we to confine our view to human happiness? The former view is the one adopted by Bentham and Mill, and (I believe) by the Utilitarian school generally: and is obviously most in accordance with the universality that is characteristic of their principle. It is the Good Universal, interpreted and defined as ‘happiness’ or ‘pleasure,’ at which a Utilitarian considers it his duty to aim: and it seems arbitrary and unreasonable to exclude from the end, as so conceived, any pleasure of any sentient being.

Plato’s reason for claiming that the life of the Philosopher has more pleasure than that of the Sensualist is palpably inadequate. The philosopher, he argues, has tried both kinds of pleasure, sensual as well as intellectual, and prefers the delights of philosophic life; the sensualist ought therefore to trust his decision and follow his example. But who can tell that the philosopher’s constitution is not such as to render the enjoyments of the senses, in his case, comparatively feeble?

[T]he history of thought […] reveal[s] discrepancy between the intuitions of one age and those of a subsequent generation. But where the conflicting beliefs are not contemporaneous, it is usually not clear that the earlier thinker would have maintained his conviction if confronted by the arguments of the later. The history of thought, however, I need hardly say, affords abundant instances of similar conflict among contemporaries; and as conversions are extremely rare in philosophical controversy, I suppose the conflict in most cases affects intuitions—what is self-evident to one mind is not so to another. It is obvious that in any such conflict there must be error on one side or the other, or on both. The natural man will often decide unhesitatingly that the error is on the other side. But it is manifest that a philosophic mind cannot do this, unless it can prove independently that the conflicting intuitor has an inferior faculty of envisaging truth in general or this kind of truth; one who cannot do this must reasonably submit to a loss of confidence in any intuition of his own that thus is found to conflict with another’s.