But although it thus appears sufficiently evident that my “misapprehensions” of his linguistic conclusions are as unimportant in relation to the theory of descent as they are few—and, I think, also excusable—in themselves, it is impossible to doubt that far below the level of Sanskrit roots, and far beyond the range of philological science, there is a wide difference of opinion between us. For when he passes from the “Science of Language” to the “Science of Thought,”—when he quits his sphere as a philologist to enter that of the philosopher,—he persistently and consistently affirms that what he calls “the old barrier between man and beast” remains, and that he is as yet unable to perceive how it can ever be removed. This barrier of course is predicative language—the obverse side of conceptional thought; and the firm opinion thus expressed by so eminent a philologist is not only of weight _per se_, but is rendered more so on account of the manifest freedom from prejudice with which it is associated. It is on this account that I devoted so much space in my book on “Mental Evolution” to a consideration of his views; and therefore I am sorry that his present reply has not been directed to meeting my criticisms on this really important matter of philosophical doctrine, rather than to indicating “misapprehensions” with regard to such merely trivial matters of a purely philological kind as those which I have here been dealing with. But perhaps at some future time he may give me the benefit of his criticism upon my work as a whole, or not merely on the fringes of such details as really have no bearing on the objects of that work. And, if he should ever see his way to doing this, I am quite sure that the discussion would be one of a friendly character. For the points at issue would all have reference to that large and vague domain of speculative theory touching “the origin of human faculty,” where it is inevitable—and, in my judgment, even desirable—that wide differences of opinion should obtain. We are but at the commencement of a great and obscure problem, which only in our own generation has been presented by the science of biology to the contemplation of philosophy. Therefore it would be folly indeed if any man were to regard his own opinions upon it as other than provisional—and even more foolish if he were to introduce any “_meum_ and _tuum_ into these discussions.”