Locke was right; the desire to avoid pain is even stronger than the desire to find pleasure. In this way evil leads to good; for pain, which is a kind of evil, creates effort, and effort creates mind. This is the general rule. A particular example of it is, that want of food, which is one of the most serious of evils, leads to good. By contriving that the earth shall produce food only in small quantities, and in reward of labour, God has provided a perpetual spur to human progress. This is the key to the puzzle of population. By nature man is a lotos-eater till hunger makes him a Ulysses. Why should he toil, the roof and crown of things? Mainly because, if he does not toil, neither can he live; the lotos country will soon be over-peopled, and he must push off his bark again. “The first awakeners of the mind are the wants of the body,” though, once awakened, the mind soon finds out wants beyond the body, and the development of intellect and civilization goes on indefinitely.[65] The people “tend to increase” more quickly than their food, not in order that men may suffer, but in order that they may be roused to save themselves from suffering. The partial ill of all such general laws is swallowed up in the general good; and the general good is secured in two ways: humanity is developed; the resources of the world are developed. In the first place, the intellect of individual men is developed, for the constancy of nature is the foundation of reasoning, and human reason would never be drawn out unless men were absolutely unable to depend on miracles, and were obliged as well as able to make calculations on the basis of a constant law. To this constancy of nature we owe the immortal mind of a Newton. In the second place, the world must be peopled. If savages could have got all their food from one central spot of fertile ground, the earth at large would have remained a wilderness; but, as it is, no one settlement can support an indefinite increase of numbers; the numbers must spread out over the earth till they find room and food. If there were no law of increase, a few such careers as Alexander’s or Tamerlain’s might unpeople the whole world; but the law exists, and the gaps made by any conqueror, or by any pestilence, are soon filled to overflowing, while the overflowing flood passes on to reclaim new countries.[66]