It's pretty clear that you don't get to keep your knowledge of the world as it is today - if you did, the question would collapse to "Do you support slavery?" w

It's pretty clear that you don't get to keep your knowledge of the world as it is today - if you did, the question would collapse to "Do you support slavery?" which is much less interesting. Asking what your ancestors believed is also a bit of a miss. My ancestors in the US were all German-American, and German-Americans overwhelmingly opposed slavery, so my ancestors probably opposed it, and I probably would have opposed it too if I had been part of that population, but that's obviously a total cop-out. So take the framing of, say you were born into a white slave-owning family in the antebellum American South. Would you have freed your slaves and joined the abolitionist movement? The actual people in that situation weren't entirely a monolith - surely at least a few of them actually did that. But if the actual share who did so was, say, 1% of the population, then you have to think you're in the top 1% in terms of some combination of empathy, racial tolerance, forward-thinkingness, etc. to claim that you would. The question is useful because we're not different than people 200 years ago, no matter how much we like to think we are. I think the obvious and more explicit follow-up question is even better though - "What beliefs do you hold today that will be viewed as negatively 200 years from now as slavery is today?" If the answer is "none," we must be in such a utopia to have finally reached the end-state of human moral development.