In yet another direction, consider how central religious belief was for both abolitionists and slave owners in either their prosecution or their defense of slavery.
True, the Bible did not prohibit it, and the Old Testament is full of examples of slavery being written of and viewed in a favorable light. Abolitionists can just as easily refer to the New Testament and the teachings of Jesus and his Disciples for quick condemnation of slavery and its inhumanities.
Slaveowners also tended to believe that while a lower form of being than whites, slaves nonetheless had souls, and it was their duty as slaveowners to Christianize them (although they would be prohibited from preaching after the Nat Turner rebellion), and therefore, slavery was justified as the duty of every Christian slaveowner and as the only way for a black slave to enter the Kingdom of Heaven. Ironically, the Christian religion was one of the few sources of both unity and hope for southern slaves throughout the antebellum 1800's.
Whatever argument you make, therefore, should have religion at the center of it.
The previous post was very lucid in its approach. I would like to posit another set of ideas. In the pro- slavery position, I would advocate the idea of individual state autonomy. The loaded issue of the day, slavery evoked much in the way of the notion of "state's rights," and many slave owners used the idea of preserving their own sense of economic rights as a way to continue the practice. In their minds, the issue was not a moral one, but rather economic. In terms of articulating the anti- slavery issue, the moral focal point will be brought out. I would also invoke a historical tradition aspect of America, meaning that the nation predicated upon the founding of individual freedom cannot reconcile such a history with the presence of slavery. It is rather open ended in the way it is phrased, but I think that researching individuals from the particular time period who believed in the pro- and anti- positions would be able to generate much in the way of determining what would be supports for each side.
I'll take the anti-slavery approach.
1. God does oppose slavery. The slavery found in the New Testament was of a very different kind. It was not racially motivated and slaves could grow in great power. Also, they could become free. Also, slavery was worse than being poor. Any Roman source will show this.
2. It is morally wrong to own people, created in the image of God. Paul says that all are equal. Galatians 3:28.
3. No dynamic of human exploitation is right. Also where do you draw the line?
Sort of an open-ended question... I'll choose to give arguments for slavery and I'm assuming that I am talking as a person from the antebellum period. So I'm not claiming I believe this stuff, just that people back then would have.
- Slavery is no worse for slaves than wage labor is for workers. Slaves are cared for when sick, when hurt, and when too old to work. Wage laborers in the North are not -- they're on their own in all those times.
- God does not oppose slavery. There is nothing in the Bible that prohibits it.
- Blacks are better off in slavery. They are not capable of taking care of themselves in freedom (again -- this is not my opinion!!!)
- Since blacks are here in the America, we have to keep them enslaved because blacks and whites can not live together as equals.
These are some of the major arguments that were put forth to defend slavery in the South. Numbers 1 and 3 argue that slavery is positively good, the other two argue that it's at least not wrong in the current situation.