“I am amazed at what you say,” said I, “but there must be a limit. Let me see, if 600,000,000 are doubled three times it will amount to 4,800,000,000. Is it possible the land could produce food and clothing for so many; and yet from what you say about the rate of increase that enormous number of people will be in this country before the end of the twenty-first century.” “We will not cross that bridge till we come to it,” he answered, “we will explain that when we come to look forward into the twenty-first century. It is true we shall find a limit. The breeding instinct of any race of animals, not excepting man, would if unchecked and unopposed in the course of time absolutely fill up the earth till it could support no more. Man has for many ages been the dominant animal of the earth. Yet he has failed to stock the world to its capacity or anywhere near it for reasons you can easily supply yourself. In the first place the profession of arms or the art of keeping down the population by war has always held the most honorable rank among human employments; second the human race has been the absolutely helpless victim of pestilence and plague. Hundreds of different kinds of microbes, vibrios, bacteria and zymases have from age to age apparently whenever they saw fit, or thought men were getting too numerous, unseen and unsuspected, planted their colonies in their vital organs, and swarmed in their blood, living at their expense and sweeping them to death by myriads and millions. Next, men were at the mercy of the elements both on sea and land. Whenever a crop failed from drought or flood there followed a famine, and millions were periodically swept away by gaunt starvation, because there was no way of conveying to a needy district, the superabundance that might exist in another. But even where all nature was favorable, and nations happened to be at peace there was always the native and hereditary stupidity of the individual that blinded him to all rational ways of taking care of himself or his dependents and made it impossible for him to rear to maturity more than one out of five of his children. Thus many causes conspired to kill people off almost as fast as they were born and sometimes faster, and many times to prevent them from being born when they ought to have been. These inimical causes have all practically been eliminated. The destructive agencies supplied by nature for limiting the increase of the population having been set at defiance by art, it is evident that art must likewise find a way for limiting the increase of population, or else sometime in the future that increase will by its very success put a stop to itself, and the brutal methods of untamed nature again assert themselves. After all, art is only a subdivision of nature. It may modify the action of nature as to details, but cannot set aside the principles that govern it.”