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The article presents Leibniz's preoccupation (in 1675?6) with the difference between the notion of infinite number, which he regards as impossible, and that of the infinite being, which he regards as possible. I call this issue ?Leibniz's Problem? and examine Spinoza's solution to a similar problem that arises in the context of his philosophy. ?Spinoza's solution? is expounded in his letter on the infinite (Ep.12), which Leibniz read and annotated in April 1676. The gist of Spinoza's solution is to distinguish between three kinds of infinity and, in particular, between one that applies to substance, and one that applies to numbers, seen as auxiliaries of the imagination. The rest of the paper examines the extent to which Spinoza's solution solves Leibniz's problem. The main thesis I advance is that, when Spinoza and Leibniz say that the divine substance is infinite, in most contexts it is to be understood in non-numerical and non-quantitative terms. Instead, for Spinoza and Leibniz, a substance is said to be infinite in a qualitative sense stressing that it is complete, perfect and indivisible. I argue that this approach solves one strand of Leibniz's problem and leaves another unsolved.

Leibniz used Descartes’ strict notion of substance in “That a Most Perfect being is Possible” to characterize God but did not intend to undermine his own philosophical views by denying that there are created substances. The metaphysical view of substance in this passage is Cartesian. A discussion of radical substance without any sort of denial in the possibility of other substances does not indicate Spinozism. If this interpretation is correct, then the passage is neither anomalous nor mysterious. There is reason to believe that the passage expresses just the beliefs that we should expect Leibniz to hold in his De Summa Rerum period. Furthermore, this interpretation indicates that while Leibniz’s metaphysics during this stage of his career is suggestively similar to Spinoza’s, there is no evidence that Leibniz accepted Spinoza’s pantheistic conclusion.

Toward the end of 1676 Leibniz met Spinoza a number of times. In one of those meetings Leibniz presented a proof of the possibility of God's existence. In his proof Leibniz presupposed that a proposition is necessarily true only if its truth is either demonstrable or self-evident and that the divine perfections are simple and affirmative qualities. I contend that Leibniz's presuppositions undermine, rather than establish, the necessary existence of 'a God of the kind in whom the pious believe'. My assessment is based upon a consideration of Leibniz's argument in the context of other early papers, works written before the "Discourse on Metaphysics" in 1686.

entry for the Stanford Encyclopedia of Philosophy (SEP) This entry will attempt to provide a broad overview of the central themes of Leibniz’s philosophy of physics, as well as an introduction to some of the principal arguments and argumentative strategies he used to defend his positions. It tentatively includes sections entitled, The Historical Development of Leibniz’s Physics, Leibniz on Matter, Leibniz’s Dynamics, Leibniz on the Laws of Motion, Leibniz on Space and Time. A bibliography arranged by topic is also included. A working draft is available here (comments, as always welcome): draft.

In the main article on Leibniz, it was claimed that Leibniz's philosophy can be seen as a reaction to the Cartesian theory of corporeal substance and the necessitarianism of Spinoza and Hobbes. This entry will address this second aspect of his philosophy. In the course of his writings, Leibniz developed an approach to questions of modality—necessity, possibility, contingency—that not only served an important function within his general metaphysics, epistemology, and philosophical theology but also has continuing interest today. Indeed, it has..

READING LEIBNIZ. Context of Leibniz's philosophy -- Difficulties of reading Leibniz -- Using this book -- GOD AND THE BEST POSSIBLE WORLD. Two principles of knowledge -- The existence of god -- The nature of God -- The best of all possible worlds -- SUBSTANCES. Substance in early modern philosophy -- The simplicity and unity of substance in Leibniz -- Substances as points of view on the universe -- Interaction and pre-established harmony -- RATIONAL MINDS. Minute perceptions and levels of awareness -- Necessary truths and innate ideas -- Knowledge -- identity and choice -- LEIBNIZ'S PHILOSOPHY AND LEIBNIZ AS PHILOSOPHER .

Broad, C. D. Leibniz's predicate-in-notion principle and some of its alleged consequences.--Couturat, L. On Leibniz's metaphysics.--Friedrich, C. J. Philosophical reflections of Leibniz on law, politics, and the state.--Curley, E. M. The root of contingency. Furth, M. Monadology.--Hacking, I. Individual substance.--Hintikka, J. Leibniz on plenitude, relations, and the "reign of law."--Ishiguro, H. Leibniz's theory of the ideality of relations.--Kneale, M. Leibniz and Spinoza on activity.--Koyré, A. Leibniz and Newton.--Lovejoy, A. O. Plenitude and sufficient reason in Leibniz and Spinoza.--Mates, B. Leibniz on possible worlds.--Russell, B. Recent work on the philosophy of Leibniz.--Wilson, M. D. On Leibniz's explication of "necessary truth.".

I consider Leibniz's thoughts about Hobbes's materialism, focusing on his less-discussed later thoughts about the topic. Leibniz understood Hobbes to have argued for his materialism from his imagistic theory of ideas. Leibniz offered several criticisms of this argument and the resulting materialism itself. Several of these criticisms occur in texts in which Leibniz was engaging with the generation of British philosophers after Hobbes. Of particular interest is Leibniz's correspondence with Damaris Masham. Leibniz may have been trying to communicate with Locke, but ended up discussing Masham's version of the argument for materialism that Leibniz attributed to Hobbes.

That Leibniz finds the philosophy of Spinoza horrifyingly wrong is obvious to anyone who reads Leibniz’s work; that Leibniz finds Spinozism so seductive that his own system is in danger of collapsing into it is less obvious but, I believe, equally true. The difference here is not so much between an exoteric and an esoteric philosophy suggested by Russell2 but between a thorough-going rationalism on the part of Spinoza and Leibniz’s “mitigated rationalism” – mitigated by the exigencies of his orthodox Christianity. In other words, it is Leibniz’s traditional view of the nature of God and his creatures that leads him to abhor Spinoza’s vision, while his own commitment to a number of principles and ideas pushes him to rationalism. And if Kant is right that the mind naturally desires a system, then Leibniz ought to see the Spinozistic consequences of many of his philosophical principles. Of course, there is nothing new in saying that the God of Spinoza and the God of Leibniz are fundamentally different, but I believe that if we focus on Leibniz’s critique of Spinoza’s account of the nature of God and a constellation of related concepts, we can come to a deeper understanding of the thought of both philosophers.