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. In order that the points of difference on which these arguments are founded might be brought out into clear relief, I began by briefly considering the points of resemblance between the human mind and mind of lower orders. Here we saw that so far as the Emotions are concerned no difference of kind has been, or can be, alleged. The whole series of human emotions have been proved to obtain among the lower animals, except those which depend on the higher intellectual powers of man—_i.e._ those appertaining to religion and perception of the sublime. But all the others—which in my list amount to over twenty—occur in the brute creation; and although many of them do not occur in so highly developed a degree, this is immaterial where the question is one of kind. Indeed, so remarkable is the general similarity of emotional life in both cases—especially when we have regard to the young child and savage man—that it ought fairly to be taken as direct evidence of a genetic continuity between them. And so, likewise, it is with Instinct. For although this occurs in a greater proportion among the lower animals than it does in ourselves, no one can venture to question the identity of all the instincts which are common to both. And this is the only point that here requires to be established. Again, with respect to the Will, no argument can arise touching the identity of animal and human volition up to the point where the latter is alleged to take on the attribute of freedom—which, as we saw, under any view depends on the intellectual powers of introspective thought. There remain, then, only these intellectual powers of introspective Thought, _plus_ the faculties of Morality and Religion. Now, it is evident that, whatever we may severally conclude as touching the distinctive value of the two latter, we must all agree that a prime condition to the possibility of either resides in the former: without the powers of intellect which are competent to frame the abstract ideation that is concerned both in morals and religion, it is manifest that neither could exist. Therefore, in logical order, it is these powers of intellect that first fall to be considered. In subsequent parts of this work I shall fully deal both with morals and religion: in the present part I am concerned only with the intellect.