Between these two extremes a middle term is interposed, and from the general idea of ‹Activity› spring the more precise ideas of pain, effort, fatigue, labour, production. In analyzing ‹Sensibility› and ‹Activity› we encounter a word common to both; the word ‹Pain›. To experience certain sensations is a ‹pain›, and we cannot put an end to it but by an effort, which is also a ‹pain›. We ‹feel pains›; we ‹take pains›. This advertises us that here below we have only a choice of evils. In the aggregate of these phenomena all is ‹personal›, as well the Sensation which precedes the effort, as the Satisfaction which follows it. We cannot doubt, then, that ‹Personal interest› is the great mainspring of human nature. It must be perfectly understood, however, that this term is here employed as the expression of a universal fact, incontestable, and resulting from the organization of man,—and not of a critical judgment on his conduct and actions, as if, instead of it, we should employ the word ‹egotism›. Moral science would be rendered impossible, if we were to pervert beforehand the terms of which it is compelled to make use. Human effort does not always come necessarily to place itself between the sensation and the satisfaction. Sometimes the [p069] satisfaction comes of its own accord. More frequently the effort is exercised upon ‹materials›, by the intervention of ‹forces› which nature has placed gratuitously at our disposal. If we give the name of ‹Utility› to all which effects the satisfaction of wants, there are, then, utilities of two kinds:—one, vouchsafed to us gratuitously by Providence; the other (if I may use the expression), requiring to be purchased by an ‹Effort›. Thus the complete evolution embraces, or may embrace, these four ideas: Wants {Gratuitous Utility, Onerous Utility} Satisfaction. Man is endued with progressive faculties. He compares, he foresees, he learns, he reforms himself, by experience. If want is a ‹pain›, effort is a ‹pain› also, and there is therefore no reason why he should not seek to diminish the latter, when he can do so without diminishing the satisfaction, which is his ultimate object. This is the reason of his success when he comes to replace ‹onerous› by ‹gratuitous Utility›, which is the perpetual object of his search. It follows from the ‹interested› nature of the human heart, that we constantly seek to increase the proportion which our Satisfactions bear to our Efforts; and it results from the intelligent nature of our mind that we manage at each step to augment the proportion which gratuitous bears to onerous Utility. Every time a success of this nature is achieved, a part of our efforts is, so to speak, rendered disposable, and we have the option of either indulging ourselves with longer repose, or of working for the satisfaction of new desires, if these are strong enough to stimulate our activity.