He does not tell us what philosophy is, though he selects some allegedly philosophical problems and some metaphilosophical positions as examples of unresolvable philosophical disputes.
I want you to listen to him and read his article. Afterwards I will give you my commentary.
Erich Dietrich, “There Is No Progress in Philosophy, Essays in Philosophy, 12:329-344 (2011).
The first thing that I would like to say is that his view of philosophy is too narrow or myopic. The broader view is that philosophy is really “philosophizing.” It is an activity whose goal is to resolve disputes and hopefully to come to agreements. This activity is called by Mortimer J. Adler “dialectic.” See his book: Dialectic (1927). A related approach can be called “critical philosophy,” as presented by C.D. Broad in “Critical and Speculative Philosophy,” Contemporary British Philosophy (1924): 77-100.
See also my: The Aim of Liberal Education (2003)
As with any activity, a critical discussion can be done with various degrees of proficiency. In this sense, there can be progress in the acquisition of such a proficiency.
As to solving problems, I will mention some which have been solved.
The first is the clarification that existence is not a predicate. This solution has been attributed to Kant, but there are better modern expositions. And since this matter is relevant to an argument for God’s existence, see: C. D. Broad, “The Validity of Belief in a Personal God,” Hibbert Journal 24 (1925): 32-48.
The second concerns the credibility of miracles. See: C. D. Broad, “Hume’s theory of the credibility of miracles,” Proceedings of the Aristotelian Society, vol. 17 (1916-1917), pp. 77-94.
The third concerns the problem of a free will and determinism. The solution consists of reframing the problem as contrasting doing something freely with being coerced to do something. This solution is referred as “compatibilism.”
In short, there has been progress in philosophy in discarding superstitions and the cobwebs of language.
1. He takes Aristotle as a “paradigm?” philosopher. But is Aristotle a philosopher because he has scientific speculations? Aristotle, qua scientist was wrong about many things. And, Aristotle qua philosopher has also been criticised by other philosophers, and if these other philosophers are correct, then philosophical speculation has indeed advanced.
2. As an example of philosophy not having resolved any philosophical problems, he assumes that as to the question whether there is a God or not, there is no solution. Here he is wrong. The fact that there are people who disagree, what does that show? Can their reasoning be evaluated? Yes, relative to some agreed to standards, such as non-contradiction and compatibility with the findings of science. I pose to you the problem of finding fault with the reasoning of C. D. Broad, “The Validity of Belief in a Personal God,” Hibbert Journal 24 (1925): 32-48.
3. On the assumption that philosophy does not progress, he cites three philosophers who try to answer why this is so: Colin McGinn, Thomas Nagel, and James Sterba. By my lights, the assumption is wrong. But it does not exclude the intractability of some sorts of questions.