Before I link to Paul Copan’s article, (H/T The Poached Egg), I want to say that I actually don’t see why atheists are so bothered by slavery, since there no such thing as morality if atheism is true. If atheism is true, then slavery isn’t wrong. It’s just unfashionable in some societies who have evolved one way, versus other societies that have evolved to think slavery is OK. Whatever has evolved is right, on atheism – there is no transcendent objective standard by which atheists can condemn any practice as wrong. They also can’t prescribe moral behavior, for at least two reasons. First, there is no reason to be moral on atheism if you get more pleasure from being immoral and you can escape the consequences. Second, there is no free will on atheism, because matter is all there is and the interactions of particles in motion is determined by the laws of physics that govern matter.
Having said that, let’s assume slavery is wrong, which it is on Christian theism, and see what Paul Copan has to say about the practice of slavery and the Old Testament.
We should compare Hebrew debt-servanthood (many translations render this “slavery”) more fairly to apprentice-like positions to pay off debts — much like the indentured servitude during America’s founding when people worked for approximately 7 years to pay off the debt for their passage to the New World. Then they became free.
In most cases, servanthood was more like a live-in employee, temporarily embedded within the employer’s household. Even today, teams trade sports players to another team that has an owner, and these players belong to a franchise. This language hardly suggests slavery, but rather a formal contractual agreement to be fulfilled — like in the Old Testament.3
Through failed crops or other disasters, debt tended to come to families, not just individuals. One could voluntarily enter into a contractual agreement (“sell” himself) to work in the household of another: “one of your countrymen becomes poor and sells himself” (Leviticus 25:47). A wife or children could be “sold” to help sustain the family through economically unbearable times — unless kinfolk “redeemed” them (payed their debt). They would be debt-servants for 6 years.4 A family might need to mortgage their land until the year of Jubilee every 50 years.5
Note: In the Old Testament, outsiders did not impose servanthood — as in the antebellum South.6 Masters could hire servants “from year to year” and were not to “rule over … [them] ruthlessly” (Leviticus 25:46,53). Rather than being excluded from Israelite society, servants were thoroughly embedded within Israelite homes.
The Old Testament prohibited unavoidable lifelong servanthood — unless someone loved his master and wanted to attach himself to him (Exodus 21:5). Masters were to grant their servants release every seventh year with all debts forgiven (Leviticus 25:35–43). A slave’s legal status was unique in the ancient Near East (ANE) — a dramatic improvement over ANE law codes: “Hebrew has no vocabulary of slavery, only of servanthood.”7
An Israelite servant’s guaranteed eventual release within 7 years was a control or regulation to prevent the abuse and institutionalizing of such positions. The release-year reminded the Israelites that poverty-induced servanthood was not an ideal social arrangement. On the other hand, servanthood existed in Israel precisely because poverty existed: no poverty, no servants in Israel. And if servants lived in Israel, this was voluntary (typically poverty-induced) — not forced.