In the real world (i. e., the world addressed by the concepts in this course), an individual will not be willing to postpone consumption indefinitely. Eternal postponement would mean no consumption at all—which would mean that Crusoe produces for no ultimate end, contradicting the very concept of production (p. 4.4:8) as well as the basic praxeological principle that human action is motivated by individual purposes. Crusoe would continue to build tree houses without receiving another value in return only if building such houses was primarily a leisure activity for him, an activity enjoyed for its own sake and itself an object of consumption (p. 4.4:8).

Because the ultimate object of production is always to receive some consumers' good, and since such a good must be consumed within a finite time, we are logically compelled to recognize a principle known as time preference: a good attained at an earlier time is more valuable than the same quantity of the identical good attained at a later time. In the absence of time preference, both consumption and production would be delayed indefinitely, and there could be no human action.