out. But whatever the logic of the question, it would and should make very little impression on the average healthy-minded individual. Our problem presents a very similar situation in which we may justly question whether a healthy-minded person should have any fear about the exhaustion of the proper number of food units that may be required, even if he is as far sighted as a conservation congress.
Soon after Malthus had written his book, his theory fell into disrepute because of the opening of the great interior plain of the United States. But thinkers soon saw that the principle was just as true as before, though the pressure of conditions was temporarily postponed. But now that we have come practically to the end of free land we seem to be nearer than ever to the threshold of the catastrophe. Even such a good thinker as Joseph L. Lee, the Boston philanthropist, feels it, for in speaking about immigration he says:
Land, however, is only one of the three factors in production. The incalculable additions to labor and capital in the last generation are so much greater contributions than more land could be that we are getting farther and farther away from, rather than nearer to, the catastrophe. To return to the analogy of the sun's heat: it is of course true that the sun can not continue to give off heat forever and remain as hot as before. But we have an interesting condition arising from the fact that though the sun is radiating its heat and thus diminishing its potential energy, yet the process of contraction which is taking place within the sun causes it to generate heat as rapidly as it is losing it, and while this is not a perpetual-motion machine, for the purposes of giving continuity of heat to the earth it is a perfectly satisfactory arrangement.
In like manner it makes no difference whether we get more land, or more productivity from the same land. Malthus found that population tended to multiply by geometrical progression, while the means of subsistence multiplied by arithmetical progression. This is true so long as the process is on an "equal dose" basis. But the conspicuous fact of modern times is that means of subsistence are multiplying at a rate which makes the multiplication of population look like the pace of the historic tortoise compared to that of Achilles, whom logic tried to keep from catching up. The logic of the law of diminishing returns is of the same type. Professor Carver shows that on a certain area of land twenty men can produce more per man than fifty, though the total production of the twenty men is but 380 bushels compared with 650 bushels produced by the fifty men. As a matter of fact, in spite of Zeno's logic we know that Achilles could overtake the tortoise, and we