Moral progress: escaping mere intuition

Slavery seems objectively wrong. Why? Because it is disproportional: it harms people a lot for benefits that are not of similar magnitude. The reason we can say that it is categorically wrong, in any society, is because we cannot imagine a benefit that could offset the evil of wholly eliminating human freedom.

At first, this appears to require a consequentialist perspective: we must be willing to harm ourselves a bit and perhaps tradition a lot for the sake of the greater good. Say we throw self interest and tradition into the mix: we weight self interest more heavily and give the loss of tradition a negative utility because we think these create many unforeseen goods themselves. Then it still seems like the good of tradition can't possibly outweigh the harms of slavery. As to self interest, it seems that we can see the possibility of a substitution for achieving the same utility (in history, economic prosperity).

Part of what living in a society means is that there are certain conditions that we must avoid in pursuing our self interest. That means that we conceive of other, non-anti-social means of achieving those same goals. (at which point the separate question What is antisocial? becomes absolutely necessary to answer).) Let's grant that we prohibit only goals that are inherently anti-social - i.e., they have as their end the suffering of others, such as other-regarding preferences. But then what if society then prohibits means that are incidentally anti-social but that are the sole means of achieving someone's perfectly acceptable goal (see religious practices)?

But we cannot conceive of any way in which slavery is such a means. After all, the slave owners in the South were able to resurrect their economy after the Civil War with paid labor alone. Nor can we conceive of a way in which banning gay rights is such a means (unless someone really buys the argument that the social/moral fabric of the society will be tattered by this), because providing gay rights hasn't undermined Christians' ability to live their "good life" at all.

It appears that, by even a loose, all-pleasing consequentialism (or cost-benefit analysis, if you will), we cannot justify slavery. Thus the abolition of slavery is indeed moral progress.

Of course, every case cannot be a simple one like slavery. For this reason, I offer the following examples that are slightly more complicated: affirmative action, abortion (some might argue), surveillance of public areas, and euthanasia. This is because we do not see clear alternatives for achieving individual goals in these cases, and there are competing interests on both sides that seem far less imbalanced than in the slavery example (though I'm not arguing that I don't have an opinion on which interests in each case are more important).