The idea of a household was different in Augustine’s time. Heck, it was different just a few hundred years ago. The states role in mediating disputes was smaller. The head of a household was responsible for resolving disputes and disciplining. He was responsible for the welfare and behavior of those under him. It was an additional responsibility. We’ve moved away from that for good reason. While I’m not saying we have to give everything a pass, it would be making a categorical error to imagine a household and the state as it is today, as if the relationship was between a homeowner and a maid staff. This was how society was ordered. It was what they knew. And again, I’m not just taking slavery as a given, this is a much broader idea of the head of household’s responsibility for what went on under his roof. The non-blood members of the household weren’t family, but they weren’t just employed people in the sense we think of today. They were part of that household, and much of the responsibility for maintaining right behavior and discipline was on the head, not the state or civil courts. It’s a different way of thinking.
Also, Augustine would not have had chattel slavery in mind when he wrote this. Wage jobs weren’t around as much like they are today. This was how the sale of labor was handled much of the time, rather than doing it by the hour.
