I came across this article in the Stone column of the NYT the other day, which, among other things, claims that over the last century critical social scientists and humanists have chipped away at the idea of truth. The author cites such thinkers as Nietzsche, Foucault, and Derrida as some of the influential thinkers from which such attempts gain support.

The author's claims here are merely informative background to their larger claim about Trump, and aren't meant to be a critique. But these same ideas are often used as the basis for attacks on what might be called postmodernism: that it professes ultimate relativism, that its proponents don't believe in facts, and so on. While I personally believe postmodernism is a vague, ill-defined, and not very helpful categorization, thinkers that are mentioned in the NYT article, such as Foucault and Derrida, are often the target of these critiques.

I think it is undeniable that philosophers like Nietzsche and Foucault question the nature and truth of facts - political ones, for example. My question, however, is whether or not these thinkers (postmodern or poststructural or what have you) profess the universal relativism that often seems levied against them. In other words, do these thinkers support an epistemological relativism? Can they be said to not believe in the possibility of truth? If so, is that belief taken up by a significant portion of critical theorists and social scientists as the NYT article claims?

Apologies for the length of this post.