Volume 49, June 2017, issue 1

This journey shall provide the reader with a simple, though complete, guide to Leibniz’s metaphysics, incidentally preventing him or her from common errors. I will start with unfolding Leibniz’s definition of a simple substance as a free acting individual substance, which, in doing so, constitutes its complete concept. This latter contains everything that happens to the individual substance, a process taking place in God’s mind by forming the possibilities as combinations of his attributes before his decision to create the best world. The totality of possibilities is divided through the compatibility relation into possible worlds. A world is a collection of all compatible individual substances. God creates the best among all possible worlds. The journey will enlighten the reader on Leibniz’s technical distinction between “possible” and “contingent”. In short, “possible” is defined by Leibniz in logical terms, as what is contradiction-free. “Contingent” is something that is, but might have been not. Just the fact that the non-being of contingent things remains possible saves Leibniz from Descartes’ and Spinoza’s determinism.

As is well known, Leibniz criticises Descartes for not having shown that God (considered as ens perfectissimum) is possible, and tries to fill this gap by proving God’s possibility on the basis of absolutely positive and simple perfections. For many readers, however, these perfections have appeared problematic or unintelligible. In my paper, I primarily want to show, that they can be made comprehensible by working out their foundations in Plato’s theory of ideas. On this basis, I want to explain, how this allows to understand the compossibility of perfections, essences or ideas (in the Leibnizian regio idearum) and how such an understanding fits into his version of the ontological proof. For this purpose, the first part of my paper follows two closely related lines of investigation. On the one hand, I focus on Leibniz’s theory of ideas and try to explain in which way he combines his criticism of Descartes’s proof with a criticism of the Cartesian understanding of clear and distinct ideas. On the other hand, I discuss his transformation of Platonic ideas into essences leading from actually existing entities to real possibilities. In order to provide a foundation for this, I start with a glance at Descartes’s ontological proof and at his replies to Caterus and Mersenne concentrating on the problem of God’s possibility. The second part of my paper will work out Leibniz’s own version of the ontological proof and its Platonic background.

Leibniz’s conception of the relativity of motion has been discussed at length for a very long time. This paper doesn’t aim to give a full solution to this question, but to contribute to the debate by clarifying how the principle of relativity is introduced, justified and used in the “Dynamica”. Four different principles are identified : one purely geometrical, and three (meta) physical principles, which express God’s wisdom : a principle of equivalence of hypotheses linked to the action/reaction principle, a Galilean principle of relativity and a general principle which apply not only to rectilinear motions but also to circular ones. I argue that to appreciate the coherence of Leibniz’ approach, we should distinguish these principles more sharply than he himself did and pay more attention to their status : are they consequences of the definition of motion, consequences of the physical laws or necessary conditions for any physical theory?

Leibniz looked upon space as an order of co-existing, independent things which differ from each other. Starting from this approach, we may ask whether two specific differences among given things - e.g. one between A and B, the other between C and D - in their turn differ from one another. Steiner, inspired by Leibniz’s approach, showed that on this second level of abstraction they indeed do. However, if we proceed to a third level of abstraction, comparing differences observed on the second stage of abstraction, we shall no longer detect any material, “palpable” difference. In short: Setting off from the co-existence of different things and analysing whether qualitative, material differences are still evident on a second and a third level of abstraction, we are led to conceive space as a system comprising three qualitatively discernible dimensions. - Concerning time, Leibniz and Steiner looked upon it as an arrangement of items succeeding one another. To understand this requires - if we follow Leibniz − to be able to perceive motion. Now, most moving items are passively driven into motion, depending on an external source which imparts the movement. In contrast to that, an actively moving thing generates within itself the impulse to modify its location in relation to other items. Within the world of sensory perceptions, “organic bodies” (i.e. organisms) are capable of self-motion to a certain extent. Nonetheless, a true primary self-motion can only be postulated of a completely independent being. Herewith, Leibniz’s approach to the origin of motion and the therein implied up-welling of time reveals itself to be intimately related to lines of thought developed by Plato, Aristotle, and Plotinus - albeit employing completely different terms.

The aim of this paper is to render a detailed analysis of the correspondence with Clarke in order to shed some light in the relationship between the Principle of Identity of Indiscernibles and the Principle of Sufficient Reason. Most of the secondary literature takes for granted that Leibniz derives the Principle of Identity of Indiscernible from the Principle of Sufficient Reason in at least some parts of the correspondence. This would render the Principle of Identity of Indiscernibles a merely contingent truth and not a necessary principle. I will argue that this interpretation is misleading, and that Leibniz never abandoned the idea that the Principle of Identity of Indiscernibles is a necessary truth. Although he is continuously using the Principle of Sufficient Reason in his argumentation, he keeps in parallel a strong argumentation that entails the necessity of the Principle of Identity of Indiscernibles. To achieve this goal, it will be necessary to point out first some contextual facts that may determine a correct understanding of the correspondence. It will be also necessary to frame the discussion about the principles into the broader debate on the possibility of Newtonian space. Finally, it will be shown that the mentioned hypothesis is supported by textual evidence throughout the entire correspondence.

During his years in Mainz Leibniz made the acquaintance of the physician Johann Hiskias Cardilucius. Later in his life he claimed that Cardilucius was identical with the alchemist Johann Fortitudo Hartprecht, who had published under the pseudonym “Filius Sendivogii”. By comparing what is known about Cardilucius and Hartprecht it will be shown that Leibniz’s claim is probably correct.