Some changes in morality come about because people notice that their previous ideas contained incorrect probability assessments. These changes can be considered moral progress.
Example: people find a logical inconsistency in their moral thinking, and correct for it.
Example: people notice that they have been assuming it necessary to be Homo sapiens or to be of a specific gender or color in order to have conscious experience, and that they don't actually have any basis for such an assumption.
As long as our knowledge about the universe (including our own thought processes and the assumptions and mistakes we are making without realising them) continues to increase at a rapid pace, it is likely that every now and then we learn something such that it causes a correction in our moral thinking. Or at some point, we may still be learning rapidly, but it may have been a really long time that we last run across something that changed our ideas about morality (such a time hasn't yet come during history).
When/if we have learned all that we possibly can (this includes thinking about stuff long enough and with sufficient quality to get all the insights that we can), there can be no more moral progress. If in such circumstances we find that we have identical ideas about morality when compared to our peers-in-knowledge (including knowledge about past life experiences of each other), and that these ideas don't change over time, it proves there was convergence in the change of our ideas about morality (the question of how much of the change was a random walk could be further studied by running ancestor simulations).
On the other hand, we might find that we still can't agree with each other about morality, not even when we are essentially omniscient. This would prove that much of the change in moral ideas is a random walk, and that possibly only a small fraction of the changes can be considered progress.
And, it does even currently seem to me, that it is logically possible to be essentially omniscient, and have really weird utility functions. But perhaps very few of us humans ever want to change ourselves into beings with very weird utility functions, and most of us will indeed converge to some specific ideas about morality.
(I guess I should confess that my thinking expressed here has been heavily influenced by Eliezer's previous writings.)
Followup to: Is Morality Preference?
In the dialogue "Is Morality Preference?", Obert argues for the existence of moral progress by pointing to free speech, democracy, mass street protests against wars, the end of slavery... and we could also cite female suffrage, or the fact that burning a cat alive was once a popular entertainment... and many other things that our ancestors believed were right, but which we have come to see as wrong, or vice versa.
But Subhan points out that if your only measure of progress is to take a difference against your current state, then you can follow a random walk, and still see the appearance of inevitable progress.
One way of refuting the simplest version of this argument, would be to say that we don't automatically think ourselves the very apex of possible morality; that we can imagine our descendants being more moral than us.
But can you concretely imagine a being morally wiser than yourself—one who knows that some particular thing is wrong, when you believe it to be right?
Certainly: I am not sure of the moral status of chimpanzees, and hence I find it easy to imagine that a future civilization will label them definitely people, and castigate us for failing to cryopreserve the chimpanzees who died in human custody.
Yet this still doesn't prove the existence of moral progress. Maybe I am simply mistaken about the nature of changes in morality that have previously occurred—like looking at a time chart of "differences between past and present", noting that the difference has been steadily decreasing, and saying, without being able to visualize it, "Extrapolating this chart into the future, we find that the future will be even less different from the present than the present."
So let me throw the question open to my readers: Whither moral progress?
You might say, perhaps, "Over time, people have become more willing to help one another—that is the very substance and definition of moral progress."
But as John McCarthy put it:
Once you make "People helping each other more" the definition of moral progress, then people helping each other all the time, is by definition the apex of moral progress.
At the very least we have Moore's Open Question: It is not clear that helping others all the time is automatically moral progress, whether or not you argue that it is; and so we apparently have some notion of what constitutes "moral progress" that goes beyond the direct identification with "helping others more often".
Or if you identify moral progress with "Democracy!", then at some point there was a first democratic civilization—at some point, people went from having no notion of democracy as a good thing, to inventing the idea of democracy as a good thing. If increasing democracy is the very substance of moral progress, then how did this moral progress come about to exist in the world? How did people invent, without knowing it, this very substance of moral progress?
It's easy to come up with concrete examples of moral progress. Just point to a moral disagreement between past and present civilizations; or point to a disagreement between yourself and present civilization, and claim that future civilizations might agree with you.
It's harder to answer Subhan's challenge—to show directionality, rather than a random walk, on the meta-level. And explain how this directionality is implemented, on the meta-level: how people go from not having a moral ideal, to having it.
(I have my own ideas about this, as some of you know. And I'll thank you not to link to them in the comments, or quote them and attribute them to me, until at least 24 hours have passed from this post.)
Part of The Metaethics Sequence
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