In order to establish the principle that slavery, in any part of the United States, is destined to be an exception to that general law which decrees universal emancipation as a certain result, it would be necessary to show the negro to be incapable of improvement; for if he be destined to progressive existence at all, it follows that, sooner or later, he will reach a condition in which he no longer can or ought to be held in subjection or subordination of any kind; and this, too, without the supposition of any moral change or improvement on the part of the slave owner. Indeed, the most usual and plausible, if not also the most truly substantial of all excuses or justifications for enslaving the African, in any form, has, from the beginning, been predicated on the fact that his subordination to the superior intelligence of the white man is calculated to improve him physically, morally, and intellectually. The capacity of improvement thus admitted, the logical result must be eventual liberation. This result is bound up in the very nature of things, and must inevitably be developed at some time or other, as proved by all history, as well as by any rational analysis of human character and intellect. But, only one half the argument has been employed to bring the mind to this irresistible conclusion. We have omitted all examination of the subject in that other aspect which has reference to industrial, economical, and moral considerations affecting the vital interests of the superior race. We need not say how much the discussion of these would serve to strengthen the argument and confirm the conclusion already stated.