Christianity forever changed western civilization. While the Greeks and the Romans contributed much to philosophy, governmental structure, architecture, community planning, military strategy, art, and various other secular pursuits, they didn’t contribute to the ethics or heart of the western world.
The ancients enjoyed blood sport. Over half of the population were slaves. They led aggressive wars. They were polytheists and emperor worship was demanded–upon pain of death–and there was no religious freedom. They practiced infanticide, exposing unwanted babies, especially girls, to the beasts and the elements. They were brutal and used force to control their subjects. Flogging, crucifixion, burning, impaling, and torture were commonplace. The ancient world may have had a form of order, but they were not civilized.
Piercing through the darkness of this time was the Light of the World, a simple carpenter from the middle east, Jesus of Nazareth. He would become the most powerful civilizing influence humanity has ever known.
One of the major changes brought about by Jesus was the attitude toward slavery. In Athens, where nearly three-fourths of the population were slaves, Aristotle merely looked upon them as living tools. He said that men could be possessed by other men even though they are human beings because some men are merely “instruments of action” and that it was natural for some to be slaves “for that some should rule and others be ruled is a thing not only necessary, but expedient; from the hour of their birth, some are marked out for subjection, others for rule.” He called a slave a “live article of property.”
Plato also thought that the need for slavery was a natural condition of humanity (perhaps a necessary evil), but Jesus said that he came to set the captives free! He stands alone in ancient history as the friend of the slave.
In a world that had no energy supply, slaves were a form of power. Those who owned them had a source of production, a way to earn money or obtain goods. There were those who did manual labor and those who didn’t. Work was scorned. It was looked down upon as the destiny of those in the lower class.
But when Jesus came, he changed this attitude. How? By being a common laborer — a carpenter. If the King of Glory can work with his hands, how can I despise hard work? His disciples were also common laborers. Peter was a fisherman. Paul was a tentmaker. There were no upper class disciples. They were all laborers (or in Matthew’s case, a tax collector) who would have been despised in the ancient world.
The letters of Paul also reflect this changing attitude towards labor. In his second letter to the Thessalonians, he tells the church not to feed those who won’t work even though they are able. (The Didache even says that the church should consider a traveling prophet to be false if he wouldn’t work.)  The example of Jesus made honest employment admirable, not despicable. The effect this had on the labor force was tremendous. It lessened the need for slaves because more people were now willing to work in allegiance and service to their King.
Paul also pointed out that on a spiritual level all were equal before God.
“There is neither Jew nor Greek, slave nor free, male nor female, for you are all one in Christ Jesus.” (Galatians 3:28)
This was different from the Roman religion, which wouldn’t even allow slaves to venerate their gods because they would have defiled their worship. But Christianity had such a leveling effect on society that slaves had to be encouraged to not look down on their masters. (1 Timothy 6:2) Slaves would become full members of the church. They would be treated as equals. After Peter and Paul, the next bishop of Rome was Linus, a slave. Callistus, another early bishop of Rome, was also a slave. The church, unlike the Roman empire, would recognize slave marriages, and while pagans were always sure to distinguish the tombs of the slave from the tombs of the free man, Christianity would make no such distinction.
While the church only consisted of a small band of poor, weak Jews in a huge, powerful, and somewhat monstrous empire, there was certainly no hope that they could overthrow the slave system through force or revolution. Certainly, rebellion had been tried before, and the third time it was led by Spartacus, whose forces included trained gladiators, and yet they failed. Their bodies, crucified by the thousands, would line the Appian Way for miles. Paul had no hope of overthrowing a system or empire that was capable of striking such a crushing blow.
So he taught Christians how to live as free men within the slave system–how to live above the tyranny with dignity, and for a higher purpose — the glory of God. But, beyond that, he did something else–he taught the church to live as equals. Perhaps in the outer world there was injustice to contend with, but within the walls of the church there was love and brotherhood. Thus we see Paul, writing in the letter to Philemon about Onesimus, his runaway slave:
. . . although in Christ I could be bold and order you to do what you ought to do, yet I appeal to you on the basis of love. I then, as Paul–an old man and now also a prisoner of Christ Jesus–I appeal to you for my son Onesimus, who became my son while I was in chains. Formerly he was useless to you, but now he has become useful both to you and me. I am sending him–who is my very heart–back to you. I would have liked to keep him with me so that he could take your place in helping me while I am in chains for the gospel. But I did not want to do anything without your consent, so that any favor you do will be spontaneous and not forced. Perhaps the reason he was separated from you for a little while was that you might have him back for good–no longer a slave, but better than a slave, as a dear brother. He is very dear to me but even dearer to you, both as a man and as a brother in the Lord. (Philemon 1:8-16)
These “brothers in the Lord” who were bound by love for God and one another would be equal in martyrdom also. H.G. Wells describes the effect of Christianity on the “lowly and unhappy” classes of “slaves, soldiers, and distressed peoples:”
Christianity has been denounced by modern writers as a “slave religion.” It was. It took the slaves and the downtrodden and it gave them hope and restored their self-respect so that they stood up for righteousness like men and faced persecution and torment. 
One example of a slave and free person facing martyrdom together is that of Felicity and Perpetua. Felicity was a slave girl who had just given birth in the arena jail and Perpetua was a free woman who was still nursing her baby. They were arrested and told to renounce Christ, but refused, and were sentenced to death in the Coliseum. Robert Ellsburg tells the story of their martyrdom:
Perpetua and Felicity were set in the arena together. At first they were stripped, causing the crowd to shudder “seeing one a tender girl, the other her breasts yet dropping from her late childbearing.” And so in a final ironic concession to their womanhood they were permitted to cover themselves. They were then exposed to a savage cow which tossed them about on its horns. When they had survived this ordeal the executioner was ordered to put them to the sword. . . . . A final poignant image remains. The narrator notes that before meeting the sword the two young women, formerly mistress and servant, now sisters in Christ, turned to one another before the jeering crowd and exchanged a kiss. 
Christianity was a leveler. It made all people equal before God. Age, gender, nationality, and income weren’t important in the kingdom of God. The only thing that mattered was the heart. A Christian was one who had humbly received the grace of God through Jesus and then lived a life of purity and love towards others. It didn’t matter where a person was in life. Young, old, rich, poor, black, white, educated, uneducated, male, female, Jew, Greek, slave, free. Every life was special, created by God, and worthy of love and respect.
Perpetua and Felicity would face death together, holding hands, as equals before God. This attitude permeated the church, inspiring them to be compassionate to the slave and do noble and courageous deeds in order to deliver captives out of their bondage. This virtue didn’t come from the Greek philosophers. It came from the Nazarene who said, “Whom the Son sets free, is free indeed.” (John 8:36)
The early church would go overboard to fulfill these words of Jesus. Clement described the willingness of the believers to extravagantly help others:
This great love would be written about in all the early writings of the church. Aristides, the Athenian orator, noted:
“And if they hear that anyone of their number is imprisoned or in distress for the sake of their Christ’s name, they all render aid in his necessity, and if he can be redeemed, they set him free.” 
The Shepherd of Hermas expressed this passion simply:
“Instead of fields buy souls in trouble, as each of you is able.” 
The early church may not have led a slave rebellion in the physical sense, but in the spiritual sense they were revolutionaries. They couldn’t overthrow the Empire, but they could undermine it. And the heart of Jesus would eventually prevail. Goodness would defeat evil. Freedom would conquer tyranny. Because of Jesus. To whom else can we attribute the source of the attitude found in these words of the Apostolic Confession:
All monies accruing from honest labour do ye appoint and apportion to the redeeming of the saints, ransoming thereby slaves and captives, prisoners, people who are sore abused or condemned by tyrants. 
The church would continue in this passionate thrust toward releasing captives and setting them free until slavery no longer existed as an institution.
Melania would be one of many wealthy converts, who would sell their possessions and give them to the poor. She would also be one of many who released their slaves. In her case, she is reported to have set eight thousand slaves at liberty. During the Barbarian invasions of the 5th to 7th centuries, captives from conquered cities were hauled away into slavery and the church intervened, redeeming them by the thousands.
Would the church have acted in this way if they condoned slavery? If, as many modern commentators declare, the church was indifferent to, or even advocated slavery (since Paul told the slaves in the Ephesian church to “obey their masters”), would believers have acted so extravagantly in their eagerness to set slaves free? Redemption of slaves, as the Christian had been redeemed from the bondage of sin (symbolized in the Old Testament by the Israelite deliverance from the bondage of Egypt) was such an important aspect of the mission of the early church that slavery would finally be expunged completely from the Roman Empire
 Aristotle, “Politics,” The Basic Works of Aristotle. ed. Richard McKeon (New York, Random House, 1941, 1131-1132.
 “The Didache,” Early Christian Fathers, Volume 1, trans. and ed. Cyril C. Richardson (Philadelphia: The Westminster Press, 1953), 176.
 H.G. Wells, The Outline of History: Being a Plain History of Life and Mankind, Volume I. (Garden, NY: Garden City Books, 1949), 498.
 Robert Ellsburg, All Saints: Daily Reflections on Saints, Prophets, and Witnesses for Our Time (New York: The Crossroad Publishing Co., 2005), 105.
 Clement, “Letter to the Romans,” Early Christian Fathers, Volume I, trans. Cyril C. Richardson (Philadelphia: The Westminster Press, 1952), 68.
 William Barclay, The Letter to the Hebrews (Westminster: John Knox Press, 2002), 226.
 “The Shepherd of Hermas,” Apostolic Fathers, trans. J.B. Lightfoot and ed. J.R. Harner (Grand Rapids, MI: Baker House Books, 1967.), Wesley Center Online, http://wesley.nnu.edu/biblical-studies/noncanon/fathers/ante-nic/hermas1.htm (accessed 2/23/2008).
 Barclay, Letter to the Hebrews, 226-227