question is, at what point the line is to be drawn. How far down may we come in the development of type before this principle ceases to act? Again, how can it be positively ascertained that changes of nutrition, or changes in the general balance of function, may not act on the reproductive system so as to produce inheritable variation? Mr. Wallace does well to stand up for the doctrine of natural selection, and to insist that it shall not needlessly be put aside; but the general doctrine of evolution would not suffer if the exceptions to the action of natural selection contended for by Mr. Spencer should ultimately be maintained.
Refusing to admit any other general law than that of natural selection as a key to the development of species, and finding, as he asserts, that law inadequate to explain man's moral and intellectual nature, or rather the extreme differences existing between individuals in respect to moral and intellectual qualities, Mr. Wallace summons to his assistance the theory of a special "spiritual essence of nature, capable of progressive development under favorable conditions." To explain an unknown thing by one still more unknown has never been considered a quite satisfactory logical performance; and we can not help feeling a little surprised that, in a purely scientific treatise, our author should resort to such a method. "On the hypothesis," he says, "of this spiritual nature superadded to the animal nature of man we are able to understand much that is otherwise mysterious or unintelligible in regard to him." The trouble is that "this spiritual nature," as it does not lend itself to definition, is not and can not be an object of knowledge, and therefore can not serve as a scientific hypothesis at all. It may, however, be questioned whether Mr. Wallace is not untrue to his own principles when he says that the differences in moral and intellectual attributes between different individuals are greater than can exist under the rule of natural selection. Who is to set the limits of spontaneous variation in any species, and, above all, in the most complex and highly organized species, man? In the lower tribes individuals departing in a marked manner from the average type are generally doomed to destruction; but in human society it is different. Human society is itself an organism of ever-increasing complexity as we pass from the lower to the higher races; and in the social organism there is room for an infinite variety of tastes, accomplishments, aptitudes, and powers. A man need not be a great mathematical genius or have a surpassing talent for music in order to survive; neither does an extraordinary development in either direction necessarily lead to his extinction. A place can generally be found for every man whose nature is not absolutely anti-social. Thus extreme variations are preserved, and the qualities they imply are kept, as it were, in circulation in the social body, ready to manifest themselves under suitable conditions. The range of variation in men would probably be greater than it is were it not for the fact that the law of natural selection is at work more or less at all times in suppressing both superiorities and inferiorities. It was an old pastime of a certain venerable race to stone their prophets; and one of their wisest men has left on record the caution: "Be not righteous overmuch, neither make thyself overwise: why shouldst thou destroy thyself?" Nor has the danger of excessive righteousness altogether vanished in our own time, as Mr. Spencer in his essay on "The Morals of Trade" bears impressive witness. But, on the other hand, there are dangers in excessive inferiority. After uttering his caution against over-righteousness the Hebrew moralist goes on to say: "Be not overmuch wicked, neither be thou foolish: why shouldst thou die before thy time?" And to-day, as then, the man who is