Appeared in: P. Bouquet, P. Br´ezillon, L. Serafini, M. Benerecetti, F. Castellani (Eds.), 2nd International and Interdisciplinary Conference on Modeling and Using Context (CONTEXT’99). LNAI 1688, Springer, pages 242–255, 1999. In this paper, an application of automated theorem proving techniques to computational semantics is considered. In order to compute the presuppositions of a natural language discourse, several inference tasks arise. Instead of treating these inferences independently of each other, we show how integrating techniques from formal approaches to context into deduction can help to compute presuppositions more efficiently. Contexts are represented as Discourse Representation Structures and the way they are nested is made explicit. In addition, a tableau calculus is present which keeps track of contextual information, and thereby allows to avoid carrying out redundant inference steps as it happens in approaches that neglect explicit nesting of contexts.