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ix LIMITS OF NATURAL SELECTION IN MAN 187limits ;and that just as surely as we can trace the action ofnatural laws in the development of organic forms, and canclearly conceive that fuller knowledge would enable us tofollow step by step the whole process of that development, sosurely can we trace the action of some unknown higher law,beyond and independent of all those laws of which we haveany knowledge. We can trace this action more or less distinctlyin many phenomena, the two most important of whichare the origin of sensation or consciousness, and the developmentof man from the lower animals. I shall first considerthe latter difficulty as more immediately connected with thesubjects discussed in this volume.WJrnt Natural Sehctim can Not doIn considering the question of the development of man byknown natural laws, we must ever bear in mind the first principleof natural selection, no less than of the general theoryof evolution, that all changes of form or structure, all increasein the size of an organ or in its complexity, all greater specialisationor physiological division of labour, can only be broughtabout in as much as it is for the good of the being so modified.Mr. Darwin himself has taken care to impress upon usthat natural selection has no power to produce absoluteperfection, but only relative perfection, no power to advanceany being much beyond his fellow beings, but only just somuch beyond them as to enable it to survive them in thestruggle for existence. Still less has it any power to producemodifications which are in any degree injurious to its possessor,and Mr. Darwin frequently uses the strong expression,that a single case of this kind would be fatal to his theory.If, therefore, we find in man any characters, which all theevidence we can obtain goes to show would have been actuallyinjurious to him on their first appearance, they could notpossibly have been produced by natural selection. Neithercould any specially developed organ have been so producedif it had been merely useless to him, or if its use were notproportionate to its degree of development. Such cases asthese would prove that some other law, or some other power,than natural selection had been at work. But if, further,we could see that these very modifications, though hurtful or