Abstract

The Dissertatio praeliminaris is one of the early works of Leibniz in which he proposes an elaborate critique, while presenting his own principles. In accepting several points of Nizolius's philosophy, the young Leibniz tries moreover to defend theses which have constituted the basis of many of his later theories. Three major topics will be examined in this article. First, the question of definition, which is taken from a grammar point of view, where clarity is, in fact, the only criterion to establish the signification of words in usage. Second, perhaps the most important, concerns the problem of nominalism that puts Nizolius in opposition with Leibniz: they do not agree on the determination of signification, meaning whether it stands on conventions or on mental concepts. Third, the link between demonstration and induction as a consequence of a nominalistic approach is also discussed in Leibniz's preface. We are thus better able to understand the origins of Leibniz's philosophical reflection