When I first began to study the history of slavery around the world, many years ago, one of the oddities that puzzled me was the practice of paying certain slaves, which existed in ancient Rome and in America's antebellum South, among other places.
In both places, slave owners or their overseers whipped slaves to force them to work, and in neither place was whipping a slave literally to death likely to bring any serious consequences.
There could hardly be a greater power of one human being over another than the arbitrary power of life and death. Why then was it necessary to pay certain slaves? At the very least, it suggested that there were limits to what could be accomplished by power.