Initially, white Southerners justified slavery as a necessary evil. They knew it was wrong to own other human beings, but they rationalized it as the only way to make their agrarian economy work. They didn't think they could rely on paid free labor to come to work when needed or to work cheaply enough to make agriculture profitable. Many white Southerners who were not happy with slavery also thought it would gradually fade away on its own.

However, as time passed and the cotton gin was invented, making slavery-dependent cotton crops profitable, it became more debatable whether slavery would fade away naturally. Many Northerners, as a result, became more and more militantly anti-slavery. After the publication of Harriet Beecher Stowe's Uncle Tom's Cabin, a firestorm erupted, with many Northerners demanding an immediate end to slavery.

As the situation polarized, white Southerners moved away from the "necessary evil" argument and began to increasingly argue that slavery was a positive good. They said the slaves had cradle-to-grave security and were treated better than white factory workers in the North. Southern whites also argued that blacks were childlike and unfit for freedom. They asserted that the slaves benefited from exposure to Christianity and white culture. They argued that the Bible condoned slavery.

These arguments were vehemently protested by freed slaves who had experienced the cruelty of slavery as well as by whites who asked those who thought slavery was a positive good why they didn't sell themselves or their children into slavery.

As we know, it took a war to resolve these differences and free the slaves.