In the lengthy reading of Rousseau which makes up the central portion of Jacques Derrida's Of Grammatolog. there is much that should interest philosophers of logic (Derrida 1976). Just recently some writers — Graham Priest among them — have broken the effective veto on discussion of Derrida's work in the analytic community and ventured to suggest that his proposals concerning the "logic of supplementarity" might usefully be looked at in relation to current debate about deviant, many-valued, or paraconsistent logics (Priest 1994, 1995; also Norris 2000a: 125–47, 148–71). What I aim to do here is to put the case that Derrida's commentary on Rousseau is not only an exercise in rhetorical deconstruction — or "literary" close-reading — but also, more to the point, a set-piece example of modal-logical analysis. Before that I shall discuss some salient issues that emerged from the notorious exchange (the "determined non-encounter", as Derrida ironically described it) between Derrida and John Searle on the topic of Austinian speech-act theory, a debate which has left its protagonists — as well as the rival commentators — deeply divided as to who came off best (Austin 1963; Derrida 1977a,b, 1989; Searle 1977).