I think Guattari Hero's question about the convergences, or lack thereof, between Derrida and Lyotard gets at the heart of a meta-level tension that runs through much postmodern/poststructural theory. Namely, are the developments that characterize postmodernity representative of a rupture unique to that (this?) period, or, rather, have such "developments" always "been the case," and we are just now coming to realize their validity/utility? There is probably a techinical name for this distinction; in fact, it might be postmodernism v. poststructuralism. We should ask Professor Fitzpatrick.