Five points, both historical and theological, to render credible the preaching of New Testament slavery texts:

1. Slavery in the Greco-Roman world is not to be equated, historically speaking, with antebellum American race-based chattel slavery.
2. Nevertheless, Greco-Roman slavery was, from the perspective of Christian morality, a violent, unjust, and dehumanizing system: differently shaped in the form of its evil than the American form, but reprehensible nonetheless.
3. The New Testament canon contains both (a) prudential, theologically grounded guidance for life under such a system and (b) moral and theological lessons that, developed and applied over time within a Christianizing society, should have — and largely did — inevitably resulted in the eradication of the slave system.
4. These different witnesses are not to be conflated, even when they emerge from the same texts (e.g., the book of Philemon), but neither are they in opposition to one another. The Christian tradition, drawing on this textual heritage, is right to now condemn all forms of slavery as unjust violations of divine law. Neither does this obviate the moral responsibility of those who exist within systems of slavery to adhere to Christian ways of living.
5. The fact that the New Testament and early Christian “strategy” (a misleading word in this context) for the eradication of slavery involves, in a sense, accommodating its ongoing existence during the Christianization of society is not a warrant against, in a modern society with its moral norms already re-framed by Christianization, using appropriate mechanisms of law and even force to destroy enduring systems of enslavement. To say that would be to simultaneously radically enlarge and disastrously narrow the sufficiency of Scripture.