One more reason why the unity of the human species cannot be considered a proof of equal intellectual capability of races. It is a favorite method of naturalists to draw an analogy between man and the brute creation; and, so far as he belongs to the animal kingdom, this method is undoubtedly correct and legitimate. But, with regard to man's higher attributes, there is an impassable barrier between him and the brute, which, in the heat of argument, contending parties have not always sufficiently respected. The great Prichard himself seems sometimes to have lost sight of it.[7] Thus, he speaks of "psychological" diversities in varieties of the same undoubted species of animal, though it is obvious that animals can have no psychological attributes. But I am willing to concede to Mr. Prichard all the conclusions he derives from this analogy in favor of unity of the human species. All dogs, he believes, are derived from one pair; yet, there are a number of varieties of dogs, and these varieties are different not only in external appearance, but in what Mr. Prichard would call psychological qualities. No shepherd expects to train a common cur to be the intelligent guardian of a flock; no sportsman to teach his hounds, or their unmixed progeny, to perform the office of setters. That the characteristics of every variety of dogs are permanent so long as the breed remains pure, every one knows, and that their distinctive type remains the same in all countries and through all time, is proved by the mural paintings of Egypt, which show that, 2,000 years B. C., they were as well known as in our day.[8] If, then, this permanency of "psychological" (to take Mr. Prichard's ground) diversity is compatible with unity of origin in the dog, why not in the case of man? I am far from desiring to call into question the unity of our species, but I contend that the rule must work both ways, and if "psychological" diversities can be permanent in the branches of the same species of animals, they can be permanent also in the branches of the human family. In the preceding pages, I have endeavored to show that the unity of species is no proof of equal intellectual capability of races, that mental imparities do not conflict with the universality of the gospel tidings, and that the permanency of these imparities is consistent with the reasoning of the greatest expounder of the unity theory. I shall now proceed to state the facts which prove the intellectual diversities among the races of man. In doing so, it is important to guard against an error into which so many able writers have fallen, that of comparing individuals rather than masses.