Leibniz' Briefe an Hobbes

This article discusses Leibniz's two letters to Hobbes. The first one was not passed on to Hobbes, whereas the second one remained an unfinished draft. In his letters, Leibniz defends Hobbes against attacks that make no distinction between the abstract, general content of his theory and its application to concrete cases. On the other hand, Leibniz criticizes Hobbes as well. Against Hobbes' psychology, Leibniz contends that the idea of sense perception as a reaction that lingers on in the body is impossible without assuming the existence of a soul (which Hobbes denies). However, Leibniz misconstrues Hobbes' notion of reaction as actual motion instead of a tendency to motion, as Hobbes has it. Leibniz's further argument that material cohesion cannot be understood as a reaction to the impact of other bodies is also flawed since it only considers one body and not two, as is necessary for any reaction to take place.