To tell the truth, this summary of the postmodernists' position sounds to me more like someone's claim about what people are saying than a synopsis of a philosopher's actual view. For many years, for instance, I heard claims about Derrida's denial of the existence of objects before I finally read him and found how different his actual writings were from what people said about his writings.

So, if I may, I'd like to start by asking which postmodernists you have in mind, and which claims by them.