De Sade wrote something like 'what is right for me may very well be wrong for you'. As the slave owner might say to the slave. But why do we think slavery is wrong? Did someone tell us? It's certainly not the Bible: Jesus doesn't mention it and St Paul actually condones it. Perhaps that's how the owners and traders could happily go to church each Sunday. What do other holy book say? Perhaps we just followed Mrs Do-As-You-Would-Be-Done-By.