It will be readily comprehended what a potent agency was requisite, and what sacrifices must have been incurred, to subvert a social order so deeply implanted in the habits, prejudices, and even convictions of the whole world. To produce such effect, only the most potent causes, only the most powerful influences known to act upon human nature, could suffice. What are these? _Religion and self-interest._ For--not to encumber ourselves with subdivisions of causes--suffice it to say, that two overwhelming ones brought the change: one, the Christian dispensation, which gradually revolutionized public opinion amongst the slave-class, and among the pious and benevolent of the master-class; the other was of the gross and worldly kind, coming from quite the opposite direction, yet concurring to the same end--it was the force of selfishness. This force it was which, operating by calculations of profit and loss upon the mass of worldly-minded slave-owners, taught them, if not instinctively, at least by practical experience, that their bondmen might be made more servile and profitable slaves for them, _without the name_, than any that ever bore the name. The former or sublime Christian cause would, had it been allowed to operate freely and unalloyed with worldly selfishness, have extinguished human slavery of every form and degree from the face of the earth. The latter or more worldly cause, by turning the manumitted slaves into proletarians and mercenary drudges, only substituted a new and worse kind of slavery for the old.