Osvaldo Ottaviani

This chapter discusses the analogy between bare possibles and imaginary numbers, developed by Leibniz during his Paris years. In this period, he came to realize that imaginary quantities are not impossible in themselves, but they cannot be geometrically represented, for they cannot be ordered within the number line. Similarly, he regarded actual things as belonging to a single ‘series of things’, where each member is connected to every other by relations of position and succession. Bare possibles, on the contrary, can be placed nowhere in the series and, therefore, must be regarded as fictions (though reference to them is in a sense unavoidable, like the use of imaginary quantities in algebra). The young Leibniz does not extend the model of a ‘series of things’ to possibles, thus in this period he seems to reject the very idea of a plurality of possible worlds.

In quest’articolo, articolo prenderò in esame i passi in cui Kant descrive la monadologia leibniziana come un “concetto platonico” del mondo, ossia come una descrizione del mondo intelligibile che non ha nulla a che vedere con la spiegazione del mondo fenomenico. In generale, vorrei mostrare che quest’interpretazione non va contrapposta a quella che lo stesso Kant aveva dato nella prima Critica, dove la monadologia era caratterizzata come un “sistema intellettuale del mondo”. Per fare ciò, risponderò a due domande. La prima riguarda le ragioni che possono aver indotto Kant, in diverse occasioni, a presentare Leibniz come un precursore della teoria della soggettività dello spazio. La seconda riguarda il motivo per cui Kant associa costantemente la monadologia alla teoria platonica delle idee, mostrando come, in entrambi i casi, Kant intenda criticare qualsiasi possibilità di un transito dal mondo sensibile a quello intelligibile. Infine, cercherò di mostrare che, dietro questa lettura deflazionista della monadologia, c’è anche un’implicita autocritica alle tesi che Kant stesso ha sostenuto nella Dissertatio del 1770.

Leibniz considered the Cartesian version of the ontological argument not as an inconsistent proof but only as an incomplete one: it requires a preliminary proof of possibility to show that the concept of ‘the most perfect being’ involves no contradiction. Leibniz raised this objection to Descartes’s proof already in 1676, then repeated it throughout his entire life. Before 1676, however, he suggested a more substantial objection to the Cartesian argument. I take into account a text written around 1671-72, in which Leibniz considers the Cartesian proof as a paralogism and a petition of principle. I argue that this criticism is modelled on Gassendi’s objections to the Cartesian proof, and that Leibniz’s early rejection of the ontological argument has to be understood in the general context of his early philosophy, which was inspired by nominalist authors, such as Hobbes and Gassendi. Then, I take into account the reconsideration of the ontological argument in a series of texts of 1678, showing how Leibniz implicitly replies to the kind of criticism to the argument he himself shared in his earlier works.

We edited and translated a so far unpublished manuscript ("Sur la generation des insectes et d'autres petits animaux") drafted by Leibniz in 1714. The text is written on the same paper of the first draft of the "Monadology" and, as we show, there is a connection between these two texts of the late Leibniz, as far as in the "Monadology" , the rejection of the traditional theory of the spontaneous generation of small animals (like insects) is considered by Leibniz as a posteriori confirmation of his preformist theory. In addition to that, this piece shows that Leibniz was deeply influenced by the experimental results in biology and natural sciences, and, especially, by the works of Italian scientits of the Galilean tradition, like Francesco Redi and Antonio Vallisneri.