3. In the presence of so much suffering, the condition of slavery, in which a considerable part of the great human family has been sunk in squalor and affliction now for many centuries, is deeply to be deplored; for the system is one which is wholly opposed to that which was originally ordained by God and by nature. The Supreme Author of all things so decreed that man should exercise a sort of royal dominion over beasts and cattle and fish and fowl, but never that men should exercise a like dominion over their fellow men. As St. Augustine puts it: "Having created man a reasonable being, and after His own likeness, God wished that he should rule only over the brute creation; that he should be the master, not of men, but of beasts." From this it follows that "the state of slavery is rightly regarded as a penalty upon the sinner; thus, the word slave does not occur in the Bible until the just man Noe branded with it the sin of his son. It was sin, therefore, which deserved this name; it was not natural."(4)

4. From the first sin came all evils, and specially this perversity that there were men who, forgetful of the original brotherhood of the race, instead of seeking, as they should naturally have done, to promote mutual kindness and mutual respect, following their evil desires began to think of other men as their inferiors, and to hold them as cattle born for the yoke. In this way, through an absolute forgetfulness of our common nature, and of human dignity, and the likeness of God stamped upon us all, it came to pass that in the contentions and wars which then broke out, those who were the stronger reduced the conquered into slavery; so that mankind, though of the same race, became divided into two sections, the conquered slaves and their victorious masters. The history of the ancient world presents us with this miserable spectacle down to the time of the coming of our Lord, when the calamity of slavery had fallen heavily upon all the peoples, and the number of freemen had become so reduced that the poet was able to put this atrocious phrase into the mouth of Caesar: "The human race exists for the sake of a few."(5)

5. The system flourished even among the most civilized peoples, among the Greeks and among the Romans, with whom the few imposed their will upon the many; and this power was exercised so unjustly and with such haughtiness that a crowd of slaves was regarded merely as so many chattels-not as persons, but as things. They were held to be outside the sphere of law, and without even the claim to retain and enjoy life. "Slaves are in the power of their masters, and this power is derived from the law of nations; for we find that among all nations masters have the power of life and death over their slaves, and whatever a slave earns belongs to his master."(6) Owing to this state of moral confusion it became lawful for men to sell their slaves, to give them in exchange, to dispose of them by will, to beat them, to kill them, to abuse them by forcing them to serve for the gratification of evil passions and cruel superstitions; these things could be done, legally, with impunity, and in the light of heaven. Even those who were wisest in the pagan world, illustrious philosophers and learned jurisconsults, outraging the common feeling of mankind, succeeded in persuading themselves and others that slavery was simply a necessary condition of nature. Nor did they hesitate to assert that the slave class was very inferior to the freemen both in intelligence and perfection of bodily development, and therefore that slaves, as things wanting in reason and sense, ought in all things to be the instruments of the will, however rash and unworthy, of their masters. Such inhuman and wicked doctrines are to be specially detested; for, when once they are accepted, there is no form of oppression so wicked but that it will defend itself beneath some color of legality and justice. History is full of examples showing what a seedbed of crime, what a pest and calamity, this system has been for states. Hatreds are excited in the breasts of the slaves, and the masters are kept in a state of suspicion and perpetual dread; the slaves prepare to avenge themselves with the torches of the incendiary, and the masters continue the task of oppression with greater cruelty. States are disturbed alternately by the number of the slaves and by the violence of the masters, and so are easily overthrown; hence, in a word, come riots and ѕєdιтισns, pillage and fire.

Does the church teach that a master can kill his slave?  I am reading st. louis de montfort, and he says in section 71 that "the master of a slave has by law the right of life and death over him, so that he can sell him to anyone he chooses, or if you will pardon the comparison, kill him as he would kill his horse."  

Where has the church taught this either explicitly or implicitly?  I would like to know.

Nadir - I am not the one you have to explain this to, de montfort is the one who fails to grasp the simplicity. He is the one using such a false and scandalous analogy. That is what I am pointing out. But, unfortunately, this appears to be a conflict of interest for you; rendering you no explicit help.