But, on the other hand, if science takes it no longer into account, the error is assuredly committed of losing sight of what [p074] under all circumstances is the main, the essential thing—the result, the ‹useful effect›. In that case we overlook the strongest tendencies towards community and equality, and discover much less of harmony in the social order. If this book is destined to advance Political Economy a single step, it will be by keeping constantly before the eyes of the reader that portion of ‹value› which is successively annihilated, and recovered, under the form of ‹gratuitous utility›, by mankind at large. I shall here make an observation which will prove how frequently the sciences unite and nearly run into each other. I have just defined ‹service›. It is the ‹effort› in one man, while the ‹want› and the ‹satisfaction› are in another. Sometimes the service is rendered gratuitously, without remuneration, without any service being exacted in return. It proceeds, then, from the principle of sympathy rather than from the principle of self-interest. It constitutes gift, not exchange. Consequently it would seem to appertain not to Political Economy (which is the theory of exchange), but to morals. In fact, acts of that nature, by reason of their motive, are rather moral than economical. We shall see, however, that, by reason of their effects, they concern the science which now engages us. On the other hand, services rendered for an onerous consideration, on condition of a return, and, by reason of that motive (essentially economic), do not on that account remain excluded from the domain of morals, in so far as their effects are concerned. Thus these two branches of knowledge have an infinite number of points of contact; and as two truths cannot be antagonistic, when the economist ascribes to a phenomenon injurious consequences, and the moralist ascribes to it beneficial effects, we may affirm that one or other of them is mistaken. It is thus that the sciences verify and fortify one another. [p075] III. WANTS OF MAN. It is perhaps impossible, and, at any rate, it would not be of much use, to present a complete and methodical catalogue of human wants. Nearly all those which are of real importance are comprised in the following enumeration:— Respiration (I retain here that want, as marking the boundary where the transmission of labour or exchange of services begins)—Food—Clothing—Lodging—Preservation or re-establishment of Health—Locomotion—Security—Instruction—Diversion—Sense of the beautiful. Wants exist. This is a fact. It would be puerile to inquire whether we should have been better without wants, and why God has made us subject to them. It is certain that man ‹suffers›, and even dies, when he cannot satisfy the wants which belong to his organization. It is certain that he ‹suffers›, and may even die, when in satisfying certain of his wants he indulges to excess.