All ancient and medieval cultures had slaves. But some had more slaves than others. A slave is someone who is the property of somebody else, according to the laws of the place they live in. If you’re a slave you can be sold to somebody else, or forced to work without being paid at any kind of work your owner wants. Basically you can be treated like a horse or a cow.
Usually people who own slaves do take pretty good care of them. It’s just like people usually take good care of a cow, because it is worth a lot of money. But some people don’t. Some slave-owners certainly beat and starved their slaves. Owners took children from their parents. They killed them or sold them. And even if they were treated well, most people hated being slaves. They would rather be free to make their own choices.
From the Stone Age down into the Middle Ages, the color of your skin was not what made you a slave. Most slaves in Europe and West Asia were white. Most black people were free. (Most white people were free too, and some black people were slaves). People became enslaved in a lot of different ways. Often soldiers or their families who were captured in war (prisoners of war) were sold as slaves. It’s a way of raising money for the winning side. That’s how many people who had once been free later became slaves. Another way many people became slaves was by getting into debt. If you owed somebody money and you could not pay it, they could make you a slave. They could sell you to get the money.
Sometimes free people sold their children into slavery. Maybe they needed money and could not afford to take care of their children. Sometimes people sold themselves into slavery, because they could not feed themselves any other way. And if your mother was a slave, then you were automatically a slave also – even if your father was free.
The Greek philosopher Solon said that nobody should say he had a happy life until he was dead. Anybody who was free might later happen to become a slave. And anybody who was a slave might later become free. A few hundred years later, Aristotle did say that some people were just naturally born to be slaves, but he is the only one to say it. And he does not say that this is because of their race.
You might think that bishops and holy men and women would speak out against slavery, but this didn’t happen. Jesus, in the Bible, seems to say that if you are a slave, you should not rebel. You should obey quietly, and wait for a reward in Heaven. He says, “A student is not above his teacher, nor a slave above his master; it is enough for the student to be like his teacher, and the slave like his master.”(Matthew 10:25)
It is true that some early Christian men and women (especially women) freed their slaves. But they did it more as a way of getting rid of their property, than for the benefit of the slaves themselves. (Because Jesus said it was easier to get into Heaven if you were poor. He said that it is easier for a rope to go through the eye of a needle, than for a rich man to enter the Kingdom of Heaven).
Learn by doing: find and read some articles about modern-day slavery
How people became enslaved
More about Egyptian slavery
More about Roman slavery