§1. The first and most fundamental assumption, involved not only in the empirical method of Egoistic Hedonism, but in the very conception of `Greatest Happiness' as an end of action, is the commensurability of Pleasures and Pains. By this I mean that we must assume the pleasures sought and the pains shunned to have determinate quantitative relations to each other; for otherwise they cannot be conceived as possible elements of a total which we are to seek to make as great as possible. It is not absolutely necessary to exclude the supposition that there are some kinds of pleasure so much more pleasant than others, that the smallest conceivable amount of the former would outweigh the greatest conceivable amount of the latter; since, if this were ascertained to be the case, the only result would be that any hedonistic calculation involving pleasures of the former class might be simplified by treating those of the latter class as practically non-existent. I think, however, that in all ordinary prudential reasoning, at any rate, the assumption is implicitly made that all the pleasures and pains that man can experience bear a finite ratio to each other in respect of pleasantness and its opposite. So far as this ratio can be made definite the Intensity of a pleasure (or pain) can be balanced against its Duration: for if we conceive one pleasure (or pain), finite in duration, to be intensively greater than another in some definite ratio, it seems to be implied in this conception that the latter if continuously increased in extent---without change in its intensity---would at a certain point just balance the former in amount.
If pleasures, then, can be arranged in a scale, as greater or less in some finite degree; we are led to the assumption of a hedonistic zero, or perfectly neutral feeling, as a point from which the positive quantity of pleasures may be measured. And this latter assumption emerges still more clearly when we consider the comparison and balancing of pleasures with pains, which Hedonism necessarily involves. For pain must be reckoned as the negative quantity of pleasure, to be balanced against and subtracted from the positive in estimating happiness on the whole; we must therefore conceive, as at least ideally possible, a point of transition in consciousness at which we pass from the positive to the negative. It is not absolutely necessary to assume that this strictly indifferent or neutral feeling ever actually occurs. Still experience seems to show that a state at any rate very nearly approximating to it is even common: and we certainly experience continual transitions from pleasure to pain and vice versa, and thus (unless we conceive all such transitions to be abrupt) we must exist at least momentarily, in this neutral state.
In what I have just said, I have by implication denied the paradox of Epicurus that the state of painlessness is equivalent to the highest possible pleasure; so that if we can obtain absolute freedom from pain, the goal of Hedonism is reached, after which we may vary, but cannot increase, our pleasure. This doctrine is opposed to common sense and common experience. But it would, I think, be equally erroneous, on the other hand, to regard this neutral feeling---hedonistic zero, as I have called it---as the normal condition of our consciousness, out of which we occasionally sink into pain, and occasionally rise into pleasure. Nature has not been so niggardly to man as this: so long as health is retained, and pain and irksome toil banished, the mere performance of the ordinary habitual functions of life is, according to my experience, a frequent source of moderate pleasures, alternating rapidly with states nearly or quite indifferent. Thus we may venture to say that the `apathy' which so large a proportion of Greek moralists in the post-Aristotelian period regarded as the ideal state of existence, was not really conceived by them as ``without one pleasure and without one pain''; but rather as a state of placid intellectual contemplation, which in philosophic minds might easily reach a high degree of pleasure.