“So rounds he to a separate mind
From whence clear memory may begin,
As thro’ the frame that binds him in
His isolation grows defined.”
CHAPTER XVII.
GENERAL SUMMARY AND CONCLUDING REMARKS.
In the present treatise I take as granted the general theory of evolution, so far as it is now accepted by the vast majority of naturalists. That is to say, I assume the doctrine of descent as regards the whole of organic nature, morphological and psychological, with the one exception of man. Moreover, I assume this doctrine even in the case of man, so far as his bodily organization is concerned; it being thus only with reference to the human mind that the exception to which I have alluded is made. And I make this exception in deference to the opinion of that small minority of evolutionists who still maintain that, notwithstanding their acceptance of the theory of descent as regards the corporeal constitution of man, they are able to adduce cogent evidence to prove that the theory fails to account for his mental constitution.
Such being my basis of assumption, we began by considering the state of the question a priori. If, in accordance with our assumption, the process of organic and of mental evolution has been continuous throughout the whole region of life and of mind, with the one exception of the mind of man, on grounds of an immensely large analogy we must deem it antecedently improbable that the process of evolution, elsewhere so uniform and ubiquitous, should have been interrupted at its terminal phase. And this antecedent presumption is still further strengthened by the undeniable fact that, in the case of every individual human being, the human mind presents to actual observation a process of gradual development, extending from infancy to manhood. For it is thus shown to be a matter of observable fact that, whatever may have been the origin or the history of human intelligence in the past, as it now exists—or, rather, as in every individual case it now comes into existence—it proves itself to be no exception to the general law of evolution: it unquestionably does admit of gradual growth from a zero level, and without such a gradual growth we have no evidence of its becoming. Furthermore, so long as it is passing through the lower stages of this growth, the human mind ascends through a scale of faculties which are parallel with those that are permanently presented by what I have termed the psychological species of the animal kingdom—a general fact which tends most strongly to prove that, at all events up to the time when the distinctively human qualities of ideation are attained, no difference of kind is apparent between human and brute psychology. Lastly, not only in the individual, but also in the race, the phenomena of mental evolution are conspicuous—so far, at least, as the records of the human race extend. Whether we have regard to actual history, to tradition, to antiquarian remains, or flint implements, we obtain uniform evidence of a continuous process of upward development, which is thus seen to be as characteristic of those additional attributes wherein the human mind now surpasses that of any other species as it is of those attributes which it shares with other species. Therefore, if the process of mental evolution was interrupted between the anthropoid apes and primitive man during the pre-historic period of which we have no record, it must again have been resumed with primitive man, after which it must have continued as uninterruptedly in the human species as it previously did in the animal species. This, to say the least, is a most improbable supposition. The law of continuity is proved to apply on both sides of a psychological interval, where there happens to be a necessary absence of historical information. Yet we are asked to believe that, in curious coincidence with this interval, the law of continuity was violated—notwithstanding that in the case of every individual human mind such is known never to be the case.
In order to overturn so immense a presumption as is thus raised against the contention of my opponents on merely a priori grounds, it appears to me that they must be fairly called upon to supply some very powerful considerations of an a posteriori kind, tending to show that there is something in the constitution of the human mind which renders it virtually impossible to suppose that such an order of mental existence can have proceeded by way of genetic descent from mind of lower orders. I therefore next proceeded to consider the arguments which have been adduced in support of this thesis.