[Sidenote:  Examples:  slavery.  Relations between the sexes.] Take, for example, the institution of slavery.  It prevailed in the Roman Empire at the introduction of Christianity, as it did in Arabia at the rise of Islam.  In the Moslem code, as we have seen, the practice has been perpetuated.  Slavery must be held permissible so long as the Koran is taken to be the rule of faith.  The divine sanction thus impressed upon the institution, and the closeness with which by law and custom it intermingles with social and domestic life, make it impossible for any Mohammedan people to impugn slavery as contrary to sound morality or for any body of loyal believers to advocate its abolition upon the ground of principle.  There are, moreover, so many privileges and gratifications accruing to the higher classes from its maintenance that (excepting under the strong pressure of European diplomacy) no sincere and hearty effort can be expected from the Moslem race in the suppression of the inhuman traffic, the horrors of which, as pursued by Moslem slave-traders, their Prophet would have been the first to denounce.  Look now at the wisdom with which the Gospel treats the institution.  It is nowhere in so many words proscribed, for that would, under the circumstances, have led to the abnegation of relative duties and the disruption of society.  It is accepted as a prevailing institution recognized by the civil powers.  However desirable freedom might be, slavery was not inconsistent with the Christian profession:  “Art thou called being a servant? care not for it:  but if thou mayest be made free, use it rather."[e] The duty of obedience to his master is enjoined upon the slave, and the duty of mildness and urbanity toward his slave is enjoined upon the master.  But with all this was laid the seed which grew into emancipation. “Our Father,” gave the key-note of freedom.  “Ye are all the children of God by faith in Christ Jesus.”  “There is neither bond nor free, ... for ye are all one in Christ Jesus."[f] “He that is called in the Lord, being a servant, is the Lord’s freeman."[g] The converted slave is to be received “not now as a servant, but above a servant, a brother beloved."[h] The seed has borne its proper harvest.  Late in time, no doubt, but by a sure and certain development, the grand truth of the equality of the human race, and the right of every man and woman to freedom of thought and (within reasonable limit of law) to freedom of action, has triumphed; and it has triumphed through the Spirit and the precepts inculcated by the Gospel eighteen hundred years ago.  Nor is it otherwise with the relations established between the sexes.  Polygamy, divorce, and concubinage with bondmaid’s have been perpetuated, as we have seen, by Islam for all time; and the ordinances connected therewith have given rise, in the laborious task of defining the conditions and limits of what is lawful, to a mass of prurient casuistry defiling the books of Mohammedan