Good Christians created that [slave] trade and sustained it for three centuries—Catholic and Protestant alike. And they were happy to do so because, whether Catholic or Protestant, they heard the Bible telling them that they could. Up to the late seventeenth century, no Christians challenged the existence of slavery as an institution. If you had taken a straw poll in any Christian gathering before that date, such as from the University Church of St. Mary the Virgin in my own home city of Oxford, and asked whether slavery was evil, not a single Christian hand would have gone up to say yes, it was evil. That is because the predominant voices in the books of the Bible accept slavery as part of the God-given fabric of the world. Now it is entirely the other way round: not a single Christian alive, I think, would defend slavery, and so in this respect, all Christianity is now out of alignment with the Bible.
Diarmaid MacCulloch, All Things Made New: The Reformation and its Legacy (Oxford UP) 2016, page 9
Now one might argue that those Christians who turned against the slave trade and eventually helped abolish it were also being Biblical: that is, perhaps they argued that given that we are all made in the image of God, and that Christ died for all us humans (according to scripture) it must be nonsense to think one person has the right to treat another person as property. To “love thy neighbor as thyself” would seem to demand the abolition of slavery. But the significant point to make here is that even if anti-slavery Christians were not out of alignment with the Bible, it must be true that in order to make this turn from Biblically based slavery to Biblically based abolition these Christians would have to have been reading the Bible in a certain way—a way which saw sacred scripture as not constituting a comprehensive and explicit list of do’s and don’t’s, a way which saw scripture as giving the raw material for people to draw conclusions not explicitly supported by that same scripture. And here we find, therefor, a cautionary tale for those who challenge every moral or doctrinal statement they do not like with with the challenge, “does the Bible say that?”
Consider how jarring it must have been, after all, in the late seventeenth century, to consider on the one hand Biblical principles that were counter to slavery, but at the same time a Bible that had no explicit denunciation of such a terrible and very widespread practice in the ancient world. Surely this constitutes some kind of cognitive dissonance in scripture. But whether or not we accept the doctrine of Biblical infallibility, might we attempt some kind of dialectical reading with acceptance of slavery as the thesis, the salvation offered by Christ to all as the antithesis, and the resulting explicit denunciation of slavery as the necessary synthesis presaged by the Bible, even if not explicitly?