The truth appears to be that in closed countries the population remains more or less stationary, that Nature herself checks the birth-rate without the aid of artificial birth control, and that birthrates and death-rates are independently related to the means of subsistence. Section 6. A NATURAL LAW CHECKING FERTILITY During the past century the population of Europe increased by about 160,000,000, but it is utterly unreasonable to assume that this rate of increase will be maintained during the present century. It would be as sensible to argue that because a child is four feet high at the age of ten he will be eight feet high at the age of twenty. Moreover, there is evidence that, apart altogether from vice, the fertility of a nation is reduced at every step in civilisation. The cause of this reduction in fertility is unknown. It is probably a reaction to many complex influences, and possibly associated with the vast growth of great cities. This decline in the fertility of a community is a natural protection against the possibility of overpopulation; but, on the other hand, there is a point beyond which any further decline in fertility will bring a community within sight of depopulation and of extinction. Section 7. OVERPOPULATION IN THE FUTURE It is a fallacy to say that overpopulation is the cause of poverty and disease, and that for the simple reason that overpopulation has not yet occurred. For the growth of a nation we assume that the birth-rate should exceed the death-rate by from 10 to 20 per thousand, and it is obvious that in a _closed_ country the evil of overpopulation might appear in a comparatively short time. The natural remedies in the past have been emigration and colonisation. According to the birth controllers these remedies are only temporary, because sooner or later all colonies and eventually the earth itself will be overpopulated. At the British Association Meeting in 1890 the population of the earth was said to be 1,500 millions, and it was calculated that only 6,000 millions could live on the earth. This means that if the birth-rate throughout the world exceeded the death-rate by only 8 per thousand, the earth would be overpopulated within 200 years. It is probable that in these calculations the capacity of the earth to sustain human life has been underestimated; that the earth could support not four times but sixteen times its present population; and that the latter figure could be still further increased by the progress of inventions. But, apart altogether from the accuracy of these figures, the danger of overpopulation is nothing more or less than a myth. Indeed, the end of the world, a philosophic and scientific certitude, is a more imminent event than its overpopulation. Section 8. HOW NATIONS HAVE PERISHED