From a certain perspective, current liberal Western civilization seems to be a moral pinnacle. We have rejected slavery. We have substantially de-legitimized aggressive warfare. We have made huge progress in advancing the welfare of children. We have made huge progress toward gender and racial equality. In his 2011 book The Better Angels of Our Nature, Steven Pinker says he is prepared to call our recent ancestors "morally retarded" (p. 658). Imagine how we would react if a Westerner today were seriously to endorse a set of views that would not have been radical in 1800: denying women the vote (or maybe even advocating a return to monarchy), viewing slavery and twelve-hour days of child labor in coal mines as legitimate business enterprises, advocating military conquest for the sake of glory, etc. "Morally retarded" might seem a fair assessment!
From another perspective, though, it appears almost inevitable that the average person in any culture will see his or her own culture's values as morally superior. Suppose that the average person in Culture 1 endorses values A, B, C, and D, the average person in Culture 2 endorses values A, B, -C, and E, and the average person in Culture 3 endorses values A, -B, D, and F. The average person from Culture 1 will think, "Well the average person in my culture has A, B, C, and D right! The people in culture 2 have C wrong and really should pay attention to D rather than E, while the people in Culture 3 have B wrong and should attend to C rather than F. So my culture's values are superior." If Culture 1 is temporally more recent than Cultures 2 and 3, then our average person from Culture 1 can laud the change in values as "progress".
The problem is, of course, that it might not be progress at all, but rather only a preference for local values. Call this the Local Pinnacle Illusion. Someone from the past might suffer the same illusion looking forward at us, condemning (say) our liberal Western neglect of proper class and gender role distinctions, our relative irreligiosity, and our relative tolerance of homosexuality, masturbation, divorce, and moneylending -- calling the changes "decadence" rather than progress.
The question then is whether there's a good way to tell whether those of us with a Pinkeresque preference for contemporary liberal values are merely victims of the Local Pinnacle Illusion, or whether we really have made huge moral progress in the last few centuries or millennia. I've been thinking about whether there might be a way to explore this empirically, using the history of philosophy.
Here's my thought: The temporal picture of progress and the temporal picture of a random walk look very different. If, say, rational reflection over the very long haul tends to guide us ever closer to right moral principles, as Pinker thinks, then issue-by-issue we ought to see opinion changes over the very long haul that look like progressive trends of moral philosophical discovery. If, in contrast, all that's going on is the Local Pinnacle Illusion, trends should be relatively short-lived, due to local cultural pressures, and not consistently directional over the very long haul.
Suppose we chose twelve issues that have been broadly discussed since ancient times and that in at least some eras -- not necessarily our own -- are regarded as morally important issues. If we could chart philosophers' opinions on these issues quantitatively (e.g., from strong support for democracy to strong support for monarchy with moderate views in the middle, from strong support for gender-neutral role expectations to strong support for gender-specific role expectations, etc.), using -1 and +1 to mark the average position in the historically most extreme eras for each pole of each issue, then on a random-walk picture, we ought to see something like this pattern among those issues:
On the other hand, if there's moral progress through philosophical reflection, the chart ought to look more like this:
As you can see, many more moral issues show consistent trend directions over time and the most extreme positions tend to be held at the beginning and the end of the analysis period. The latter pattern follows from the fact that even if the initial historical position at time zero is by some objective standard moderate, as long as it is not spot on the target number, the trend over time should be roughly unidirectional toward the target number; and then the normalizing will make that initial position look extreme.
Two caveats and a final note:
Caveat 1: It will of course be difficult to code this objectively, and it's quite possible that the final outcome will vary depending on hard-to-justify coding decisions.
Caveat 2: My guess is that if we were to chart moral and political positions from the 1600s to the present we would see a chart somewhat like the second (progressive) chart, whereas if we were to chart equal time intervals back to the ancient West, we would see a more random-looking chart like the first. So which time period should be examined? A case for choosing the shorter period might be that it is only after the printing press and widespread communication of philosophical ideas that we should expect to see rationally-driven moral progress. However a consideration against choosing the shorter period is this: There might be cultural factors, such as industrialization and capitalization, that have created consistent unidirectional pressures on moral and political norms, independently of the rational case for adopting those norms; and for that reason the broader the temporal span the better.
Final note: We might be able to construct similar charts to evaluate whether there has been progress in metaphysics.
(By the way, see here for another post of mine on Pinker's intellectualist liberalism.)