One type of evidence that some claim is relevant to determining whether there has been progress in philosophy is whether philosophers have converged on answers to philosophical questions.
For example, David Chalmers (NYU) uses “collective convergence to the truth” as the central evidential factor in his “Why Isn’t There More Progress In Philosophy?” He defines “collective convergence on an answer over a period” as “the increase in degree of agreement on that answer from the start of the period to the end of the period.”
Has there been such convergence? Chalmers, basing his views in part on the results of the PhilPapers Survey, concludes that “there has not been large collective convergence to the truth on the big questions of philosophy.”
Overwhelmingly most philosophers are atheists or agnostics, which I take to be convergence to the truth. Most are compatibilist about free will and believe in it, which I also take to be convergence to the truth. Almost all believe in consciousness and most don’t have a clue how to explain it, which is wisdom.
He puts the popular perception that there isn’t convergence in philosophy down to an observational bias:
It is not that there isn’t convergence, it is that the outliers who do not converge get much more attention than the great mass of convergers, who don’t particularly stand out.
Maudlin thinks there has been moral progress, too:
Already in Republic… we have an argument—a clear and compelling rational argument—that even the highest political office should be open to women. The argument? List what it takes to be a good leader of the state, then note the conditions that distinguish the sexes. There just is zero overlap between the two lists. That is as compelling as a rational argument can be, and it follows that opening all political offices to women (much less acknowledging in law that women should have as much right to vote as men) is objective moral progress. Similarly for invidious legal restrictions by race. The civil rights movement was strict moral progress. That’s as true as 2 + 2 = 4.
The whole interview is here.
Related: “How Philosophy Makes Progress (guest post by Daniel Stoljar)“; “How Philosophy Makes Progress (guest post by Agnes Callard)“; “Why Progress is Slower in Philosophy than in Science“; “Whether Philosophical Questions Can Be Answered“; “Progress in Philosophy“; “The Intellectual Achievement of Creating Questions“; “The ‘New Questions of Philosophy’“; “We’re Going to Get More, and More Interesting, Kinds of Philosophy”; “Two Models for Expanding the Canon“; “Why Read Old Philosophy? (guest post by Katja Grace)“; “Are History’s “Greatest Philosophers” All That Great? (guest post by Gregory Lewis)“; “Lack of Philosophical Progress Owed to Procrastination, Study Hopes to Find“