Ix LIMITS OF NATURAL SELECTION IN MAN 187 
limits ; and that just as surely as we can trace the action of 
natural laws in the development of organic forms, and can 
clearly conceive that fuller knowledge would enable us to 
follow step by step the whole process of that development, so 
surely can we trace the action of some unknown higher law, 
beyond and independent of all those laws of which we have 
any knowledge. We can trace this action more or less dis- 
tinctly in many phenomena, the two most important of which 
are—the origin of sensation or consciousness, and the develop- 
ment of man from the lower animals. I shall first consider 
the latter difficulty as more immediately connected with the 
subjects discussed in this volume. 
What Natural Selection can Not do 
In considering the question of the development of man by 
known natural Jaws, we must ever bear in mind the first prin- 
ciple of natural selection, no less than of the general ‘theory 
of evolution, that all changes of form or structure, all increase 
in the size of an organ or in its complexity, all greater special- 
isation or physiological division of labour, can only be brought 
about in as much as it is for the good of the being so modi- 
fied. Mr. Darwin himself has taken care to impress upon us 
that natural selection has no power to produce absolute 
perfection, but only relative perfection,—no power to advance 
any being much beyond his fellow beings, but only just so 
much beyond them as to enable it to survive them in the 
struggle for existence. Still less has it any power to produce 
modifications which are in any degree injurious to its pos- 
sessor, 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 the 
evidence we can obtain goes to show would have been actually 
injurious to him on their first appearance, they could not 
possibly have been produced by natural selection. Neither 
could any specially developed organ have been so produced 
if it had been merely useless to him, or if its use were not 
proportionate to its degree of development. Such cases as 
these 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 
