The primary value of Unger’s critique of philosophy may be that it generates good and thoughtful responses. There was Schliesser’s the other day, and also the post by Pigliucci (though he says in a comment it was not aimed at Unger directly). Now Marcus Arvan has a more sympathetic take on what Unger is up to, and it is well worth reading.
What I agree with Unger on—and what I want to make the case for—is this: just as psychology was “mere speculation” prior to actually making predictions, the same is true of philosophy…. I think that philosophy that does not make any predictions at all is mere concept manipulation—manipulation of fundamentally indeterminate concepts that, by virtue of conceptual indeterminacy/vagueness, cannot in principle provide answers to the conceptual questions analytic philosophers ask….
Another way to put this is as follows: in the absence of determinate predictions, philosophy is little more than an exercise in battling argumentatively over how to interpret vague concepts for which there is no determinately correct interpretation (i.e. no truth at all). But now if this is right, then Unger is right. In the absence of predictions, philosophy is not about any determinate truths at all—for it is only concrete predictions that give determinacy to our concepts, latching them onto determinate phenomena in the world.
Read the whole thing at Philosopher’s Cocoon. Meanwhile, feel free to post additional responses to Unger you come across in the comments here.