It seems to me that this distinction must be kept clear if progress in the science is to be made. At every point, divergent conclusions are reached if the two view-points are merged. The distinction between statics and dynamics is, in a general way, the same as the distinction here made between the historical and the cross-section view. It is no answer to the Ricardian theory of land-rent for Carey to point out that historically, in new countries, the uplands are cultivated first, and the more fertile river-valleys later. Ricardo is talking about statics, and Carey about dynamics. Carey does not answer Ricardo, because he is talking about a different problem. The utility theorist especially has no right to leave the static view-point. All the elementary laws on which the utility theory is based are static laws. The law of satiety, of diminishing utility, is a static law, and the utility theorists are careful to point out that it holds only for an individual at a given time. It rests on nerve fatigue. Give the nerve time to rest, and utility does not sink. On the contrary, the dynamic law of wants is that wants expand. As old wants are satisfied, new wants arise, so that, in the course of time, _marginal_ utilities do not sink--the competition of new wants forces up the margins of the old wants. Moreover, with time, tastes change, habits are formed, and the same wants may grow more intense--as in the case of olives or whiskey. All this has been seen by the creators of the utility theory. Thus, Wieser: "The want as a whole of course retains its strength so long as a man retains his health; satisfaction does not weaken but rather stimulates it, by constantly contributing to its development, and, particularly, by giving rise to a desire for variety. It is otherwise with the separate sensations of the want. These are narrowly limited both in point of time and in point of matter. Anyone who has just taken a certain quantity of food of a certain kind will not immediately have the same strength of desire for a similar quantity. Within any single period of want every additional act of satisfaction will be estimated less highly than a preceding one obtained from a quantity of goods equal in kind and amount." (_Natural Value_, p. 9.) A similar statement is in Taussig's _Principles_ (I, 124), "In such cases, however, the tastes of the purchasers may be said to have changed in the interval. At any given stage of taste and popularity, the principle of diminishing utility will apply." Illustrations could be multiplied.