In our present investigation, the only topic still remaining to be taken into consideration is the problem of time, and we must demonstrate for what time periods men actually plan their requirements.
On this question, it is clear, in the first place, that our requirements for goods of first order appear to be met, with reference to a given future time period, if, within this time period, we will be in the position of having directly at our disposal the quantities of goods of first order that we require. It is different if we must meet our requirements for goods of first or, in general, of lower order indirectly (that is, by means of quantities of the corresponding goods of higher order), because of the lapse of time that is inevitable in any production process. Let us designate as Period I the time period that begins now and extends to the point in time when a good of first order can be produced from the corresponding goods of second order now at our disposal. Let us call Period II the time period following Period I and extending to the point in time when a good of first order can be produced from the goods of third order now available to us. And similarly, let us designate the following time periods III, IV, and so on. A sequence of time periods is thus defined for each particular kind of good. For each of these time periods we have immediate and direct requirements for the good of first order, and these requirements are actually met since, during these time periods, we come to have direct command of the necessary quantities of the good of first order.
Suppose, however, that we should try to meet our requirements for a good of first order during Period II by means of goods of fourth order. It is clear that this would be physically impossible, and that an actual provision of our requirements for the good of first order within the posited time period could result only from the use of goods of first or second order.
The same observation can be made not only with respect to our requirements for goods of first order, but with respect to our requirements for all goods of lower order in relation to the available goods of higher order. We cannot, for example, provide our requirements for goods of third order during Period V by obtaining command, during that time period, of the corresponding quantities of goods of sixth order. On the contrary, it is clear that for this purpose we would already have had to obtain command of the latter goods during Period II.6
If the requirements of a people for grain for the current year were not directly covered in late autumn by the then existing stocks of grain, it would be much too late to attempt to employ the available land, agricultural implements, labor services, etc., for that purpose. But autumn would be the proper time to provide for the grain requirements of the following year by utilizing the above-mentioned goods of higher order. Similarly, to meet our requirements for the labor services of competent teachers a decade from now, we must already, at the present time, educate capable persons for this purpose.
Human requirements for goods of higher order, like those for goods of lower order, are not only magnitudes that are quantitatively determined in strict accordance with definite laws, and that can be estimated beforehand by men where a practical necessity exists, but they are magnitudes also which, within certain time limits, men do calculate with an exactness sufficient for their practical affairs. Moreover, the record of the past demonstrates that, on the basis of previous experience as to their needs and as to the processes of production, men continually improve their ability to estimate more exactly the quantities of the various goods that will be needed to satisfy their needs, as well as the particular time periods within which these requirements for the various goods will arise.