The man who says that it does not matter if 15,000,000 Chinese die of famine, because in two generations the birthrate will make up the loss, has used a time perspective to excuse his inertia. A person who pauperizes a healthy young man because he is sentimentally overimpressed with an immediate difficulty has lost sight of the duration of the beggar's life. The people who for the sake of an immediate peace are willing to buy off an aggressive empire by indulging its appetite have allowed a specious present to interfere with the peace of their children. The people who will not be patient with a troublesome neighbor, who want to bring everything to a "showdown" are no less the victims of a specious present.
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Into almost every social problem the proper calculation of time enters. Suppose, for example, it is a question of timber. Some trees grow faster than others. Then a sound forest policy is one in which the amount of each species and of each age cut in each season is made good by replanting. In so far as that calculation is correct the truest economy has been reached. To cut less is waste, and to cut more is exploitation. But there may come an emergency, say the need for aeroplane spruce in a war, when the year's allowance must be exceeded. An alert government will recognize that and regard the restoration of the balance as a charge upon the future.
Coal involves a different theory of time, because coal, unlike a tree, is produced on the scale of geological time. The supply is limited. Therefore a correct social policy involves intricate computation of the available reserves of the world, the indicated possibilities, the present rate of use, the present economy of use, and the alternative fuels. But when