Osvaldo Ottaviani

This paper explores the Leibnizian doctrine of universal connection and its roots in the philosophy of Hobbes − an area surprisingly overlooked in scholarly literature. It is argued that, contrary to interpretations emphasizing Neoplatonic or Stoic influences, Leibniz’s conception is grounded in a physical dimension: the idea of the universe as a plenum in which every movement propagates infinitely. This view aligns with Hobbes’s causal determinism, particularly his theory of the “full cause,” according to which every effect results from an infinity of efficient concurring causes. The paper examines how Leibniz adopts and critically reworks Hobbesian ideas in his Paris writings, including the notion of “universal sympathy” traced back to imperceptible motions, while distinguishing himself from Hobbes by affirming the necessity of immaterial principles to explain substance and perception. In the concluding remarks, further lines of inquiry are suggested in order to better understand Leibniz’s critical reappropriation of some Hobbesian ideas in his philosophy of nature.

This paper examines an argument developed by Leibniz against physical atomism, which has been largely overlooked in the scholarship. As outlined in the Introduction, this specific argument is closely tied to Leibniz's conception of infinity and, in particular, to his theory of the universal connection of all things. The central sections analyse its principal formulation in a challenging text from 1689, highlighting its connections to key aspects of Leibniz's metaphysics, including his account of individuation and his theory of individual substances as "mirrors of the universe." After addressing a potential objection to the argument, the conclusion shows how Leibniz's reduction of physical atoms to fictions nonetheless allows for a partial and provisional rehabilitation of physical atoms.

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.

abstract: Throughout his career, Leibniz defines individual substances in different ways. In the 1680s, especially in the Discourse on Metaphysics, Leibniz develops an original definition of substance through the complete concept of an individual (CCI). Most commentators hold that the CCI fades out in Leibniz's later philosophy. Others argue that the "law of the series" (LoS) replaces the definition of an individual substance through the CCI. We argue that these definitions are complementary. Early versions of the LoS inform the development of the CCI in the 1680s and are clearly pronounced in Leibniz's later texts. We discuss several often-neglected texts that show that the CCI is still present in Leibniz's late writings. We support the complementarity thesis by suggesting that the CCI primarily characterizes possible individuals, whereas the LoS characterizes actual individuals. As such, the LoS is especially apt to highlight the dynamic traits that Leibniz ascribes to individual substances from the 1690s.

In many of his writings, Leibniz refers to Kepler’s concept of natural inertia to introduce his own idea of bodies having an intrinsic resistance to motion. This paper moves from the discussion of this concept of natural inertia as it can be found in a hitherto unpublished manuscript (ca. 1699-1700) in which Leibniz comments on Kepler’s Epitome Astronomiae Copernicanae. This manuscript shows the extent to which Leibniz sought to read Keplerian ideas through the lens of his dynamics. This text also contains one of the first references to ‘complex entelechy’, which will be crucial to Leibniz’s late account of substance. In the last section, we explore how Leibniz’s reinterpretation of Keplerian inertia must be read alongside his criticism of the Cartesian theory of matter in discussion with De Volder and Papin from the same years as our text. We also suggest that Leibniz proposed a sort of ideological reading of Kepler: by the end of the 1690s, he wanted to establish a German tradition in natural philosophy, especially in opposition to the English (i.e., Newtonian) one.

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.

This paper moves from a disagreement with those interpreters who explain Kant’s doctrine of real possibility in terms of possible worlds. It seems to me that a possible world framework is too much indebted to the Leibnizian metaphysics of modality and, therefore, cannot serve to make sense of Kant’s theses. Leibniz’s theory of possibility, indeed, has been deeply criticized in Kant’s Critique of Pure Reason (CPR). Interestingly enough, however, Kant’s principal argument for rejecting that the field of what is possible is greater than the field of what is real was already anticipated by Leibniz. However, Leibniz employed it to demonstrate that there cannot be more than one actual world only (the others being purely possible ones). Moving from this fact, I argue that there is a certain tension between what Leibniz says about the actual world and his commitment to a plurality of possible worlds conceived as ideas in God’s mind. The first part of my paper is devoted to show that such a tension can be traced back to Leibniz’s claims about the relation between the possible and the real. In the second part, then, I maintain that Kant’s theory of real possibility grows from a dissatisfaction with (and a rejection of) Leibniz’s attempted solution to the problem of characterizing a kind of possibility narrower than the merely logical one and, nonetheless, not identical with existence. Finally, I present a short account of Kant’s theory of real possibility, based on the notion of transcendental conditions as conditions of possibility of experience, showing how it works in the case of the forms of intuition.