In what precise sense is costliness here a co-determinant of value? When a good both costs pain or discomfort in its production and affords pleasure in its use, it is common custom to speak of the “cost” of the good as the exact opposite of its “utility.” But these concepts are not direct opposites. Cost consists in the subjective experiences of the producing man, and its precise opposite is pleasure or, specifically in our economic usage, satisfaction of want. But “utility” never is a precise equivalent for satisfaction. On the contrary, utility is another kind of opposite of satisfaction, being always conceived to belong to the good and not to lie within the man, except in the treatises of certain unconscious metaphysicians. In virtue of a certain combination of physical properties a good possesses a power to produce a satisfaction in a man.[243] This power, due to its physical properties, is the best conception of the good’s utility. The precise opposite of utility cannot be designated by cost, but the word “costliness” fits the need. In virtue of their physical properties, or physical and chemical relations with other external things, some goods require a large amount of change of man’s external surroundings to be effected by him in order that they may be produced. We give these goods the attribute of costliness, similar to the attribute of utility, and the relation between costliness and cost is similar to the relation between utility and satisfaction.[244] The question which now concerns us is whether in the case of freely producible goods the supply of which can be augmented at will by the application of more labor, the costliness of a good takes an equal part with its utility in determining its value. If the marginal utility of a good determines its value, marginal utility is still the mere creature of the supply of the good. The larger the supply, the lower the marginal utility. Putting the matter the way it is often stated in present-day treatises, the supply that will be produced depends upon the cost of the good, and thus at bottom cost determines value. Making a more careful statement we may say that the supply depends upon both the costliness and the utility, since Crusoe will increase the supply—the _average_ yearly supply, we should say if speaking of a crop—until the marginal cost and marginal satisfaction become equivalent. For the normal case, the increase of the number of increments of the good will entail an increase of marginal cost and a decrease of marginal utility. Both the marginal cost and the marginal utility vary when the supply is changed, but the supply tends to rest at the point of equilibrium of these two quantities, and is thus determined by them jointly.[245] If the general costliness of this grain should fall, its value would soon be lowered, for Crusoe would be led to produce more of it in order to reach the point of supply which equilibrates final cost and satisfaction. Thus