The truth of this has been demonstrated again and again. A pair of rabbits, for example, would in the most favourable circumstances increase in four or five years to a million. The roe of a cod may contain eight or nine millions of eggs. More appalling still, the female of the common flesh fly will at one time deposit 20,000 eggs. At this rate of increase it has been calculated that, in less than a year, a single pair would produce enough flies, if these were not devoured by their natural foes, to cover the whole surface of the globe to the depth of a mile and a quarter! But all this does not, of course, make it clear why in a beneficently ordered world such a necessity of slaughter should ever have been allowed to arise.
Darwin, as we have said, tried hard to take the most favourable view of the whole process. He thus concluded his chapter on the struggle for existence; "When we reflect on the struggle, we may console ourselves with the full belief that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply." And these are the words with which he concluded the Origin of Species: "Thus from the war of nature, from famine and death, the most exalted object we are capable of conceiving, namely the production of the higher animals, directly follows."
But a year or two later he shewed that his mind was by no means at rest on the matter, by writing in this strain to his friend Asa Gray:
"I own that I cannot see as plainly as others do, and as I should wish to do, evidence of design and beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice.... I am inclined to look at everything as resulting from designed laws, with the details, whether good or bad, left to the working out of what we may call chance. Not that this notion at all satisfies me.... Let each man hope and believe what he can. Certainly I agree with you that my views are not at all necessarily atheistical."[[2]]
Happily there were others who were able to see their way somewhat further than this. Romanes, in a paper which he read before the Aristotelian Society in 1889, shewed that he was reconsidering his position. He questioned whether the assertion, made by a speaker in a previous discussion, that "the fair order of Nature is only acquired by a wholesale waste and sacrifice," could be accepted as strictly true, for "how can it be said that, in point of fact, there has been a waste, or has been a sacrifice? Clearly such things can only be said when our point of view is restricted to the means (i.e., the wholesale destruction of the less fit); not when we extend our view to what, even within the limits of human observation, is unquestionably the end (i.e., the causal result in an ever improving world of types)."[[3]]
He had intended to write more fully on the subject, but did not live to do so. We only know that on the Sunday before his death he did express to Bishop Gore his entire agreement with a statement that had been made a short time before by Professor Knight, in his Aspects of Theism, to the effect that "A larger good is evolved through the winnowing process by which physical nature casts its weaker products aside, etc."[[4]] We cannot suppose that, if he had lived, he would have been content to have left the argument thus. That the end justifies the means, is scarcely a doctrine which can be accepted as the last word of an ethical defence of the constitution of the world.
No doubt there were further pleas to be put in, and we shall do well to give them their full value. There is the contention that the pleasures of life as a whole outweigh the sum of its evils. This was maintained, and we need not hesitate to say successfully maintained, by Lord Avebury, and not by him alone. Indeed Darwin had emphatically said, "According to my judgment happiness decidedly prevails."[[5]] Then there has always been urged the undoubted fact that pain, if an evil, is yet the minister of good. Browning's optimism may have carried him too far when he laid it down that "when pain ends gain ends," but it is not to be questioned that men have profited by sufferings, and that they have had to thank their pains, if only because these have served to protect them from yet greater misfortunes. There is a true wisdom in the moral of the old fable of the blacksmith, who prayed to heaven that the fire might not burn his fingers, to discover that as a result it had charred his hand to the bone. Medical science has had much to say with regard to the salutary office of pain. It has gone so far as to assert that, "the symptoms of disease are marked by purpose, and the purpose is beneficent." Nay more, "the processes of disease aim not at the destruction of life, but at the saving of it."[[6]] None the less, with what might seem a splendid inconsistency, the medical profession devotes itself untiringly to the alleviation of the symptoms and to the eradication of disease.
Again, we may be thankful to be assured that, whatever be the case with man, the lower organisms feel pain less than he does, and much less than he is often wont to imagine that they feel it. This has been argued again and again by the veteran naturalist Wallace, whose right to speak on the subject no one is likely to dispute. In his recently published book, The World of Life, he has devoted a whole chapter to answering the question, "Is Nature cruel?" and it is due to him, as well as to the importance of the problem, that we should carefully note what he has said. The following quotations may be taken as sufficiently indicating his position.
"The widespread idea of the cruelty of Nature is almost wholly imaginary."[[7]] "Our whole tendency to transfer our sensations of pain to the other animals is grossly misleading."[[8]]