Christia Mercer

In his thoughtful and generous review of my book, Leibniz’s Metaphysics: Its Origins and Development, Cees Leijenhorst accepts many of its most radical conclusions: that Leibniz’s metaphysics evolved out of an attempt to combine ideas gathered from the great philosophers of the past and to do so in a manner that would solve the theological, legal, and philosophical questions that most concerned him; that although Leibniz’s notion of substance developed out of his interpretation of the philosophy of Aristotle, his conception of the relation between God and creatures has its roots in the Platonism that he learned as a young man in Leipzig and Jena; that the views constituting the core doctrines of the mature philosophy were conceived by the time Leibniz went to Paris in early 1672; and that Leibniz rejects the reality of passive extended matter and embraces his own version of idealism as early as 1671. I am tempted to respond with a loud rodeo yell and end it at that. But because the few points on which.

Anyone interested in Leibniz, the Kabbalah, the Cambridge Platonists, Gnosticism, Platonism, or seventeenth-century metaphysics will want to read Allison P. Coudert’s Leibniz and the Kabbalah. Coudert argues that core features of Leibniz’s mature philosophy were directly influenced by the Kabbalah in general and Francis Mercury van Helmont’s Lurianic Kabbalah in particular. This is a provocative thesis to which Coudert brings an impressive amount of scholarly detective work. Her argument in brief goes as follows: there are important differences between the philosophy of Leibniz’s middle period and that of the late; some of the most distinctive features of the late philosophy are very similar to key aspects of the Lurianic Kabbalism of van Helmont, with whose works and ideas Leibniz became increasingly familiar after 1687; therefore, Leibniz’s late philosophy was significantly influenced by the thought of van Helmont.

When Bruno was burned at the stake in 1600, philosophers were still inclined to offer natural explanations in Aristotelian terms. Neither the physical proposals of Bruno himself, nor those of other prominent non-Aristotelians like Paracelsus had diminished the power of the explanatory model offered by the scholastics. For those philosophers watching the demise of Bruno in the Campo dei Fiori in Rome, the burning of the wood and its subsequent effects would have been explained adequately in terms of matter and substantial form. For such Aristotelian philosophers, all natural objects are constituted of matter and form, and natural events are explained in terms of the actualization of the potency of these two “principles of nature.” By the time Kenelm Digby composed his Two Treatises of 1644 and Thomas Hobbes his De Corpore in 1655, there was a new explanatory model available to explain such events, one that had greatly diminished the power of the scholastic model. According to the mechanical philosophy, nature is composed of matter—whether the res extensa of Descartes, the atoms of Gassendi, or one of the many less popular accounts of corporeity—whose actions and interactions cause and explain all the phenomena of nature. For the mechanist, therefore, all physical phenomena are to be explained in terms of some kind of matter and motion. Although these thinkers disagreed about how to define the material component in nature, they all took it to be entirely devoid of substantial forms. For our purposes here, it will be helpful to distinguish between first wave and second wave mechanists. A first wave mechanist is someone like Descartes, Galileo, Hobbes, or Gassendi who proposed a version of the mechanical explanatory model before 1650. A second wave mechanist is a philosopher working in the second half of the seventeenth century who accepts the mechanical explanatory model. For our purposes, it is important that many second wave mechanists were prepared to reject the scholastic explanatory model, replace it with the mechanical one, and yet were not content to accept the metaphysical grounding of the mechanical physics offered by the first wave mechanists.

Working on Leibniz’s vast essays and texts can seem overwhelming. As exciting as it is to study the details of the Monadology and Discourse on Metaphysics, the Theodicy and the letters to Arnauld, it can be terrifying to sit back and think that there are thousands of other pages of equally sublime and often more difficult philosophical material. The personal notes are particularly daunting. Because Leibniz wrote these for himself, it is often difficult to grasp his reasoning and decipher his underlying philosophical motivation: he typically neither states his most basic assumptions nor articulates how the piece he is presently writing fits into a general plan or project. Sometimes he just plays with an idea or tries out an argument. As Leibniz himself wrote about his notes: “instead of treasure..., you will only find ashes; instead of elaborate works, a few sheets of paper and some poorly expressed vestiges of hasty reflections, which were only saved for the sake of my memory.” But even Leibniz’s more polished essays can be unnerving in manuscript. These sheets—which contain deletions, additions, an enormous number of reformulations, and reconsiderations—reveal an impatient intellect hurrying to express its ideas. Because Leibniz is so often reluctant to set the stage for a philosophical proposal or to acknowledge its various implications, one often has to go well beyond the text in order to understand how the proposal at hand relates to other parts of his thought. Moreover, Leibniz encourages confusion by using one terminology in one text and an entirely different one in another. The moral to the story is clear: one cannot depend either on a single essay or on a small group of passages taken in isolation from others in the same period. When it comes to Leibniz’s writings, it is necessary to take the widest possible textual perspective.

This essay examines the basis of Leibniz’s views on the unity of corporeal substance. It draws on the analysis of Robert Sleigh, who linked the unity of Leibnizian substances to their possession of identity through change. It argues that Sleigh’s analysis leaves many questions about unity unanswered, notably the problem of how a substantial form produces unity in its associated passive principle or body, whose components are in constant flux. The key to this problem lies in a historically informed account of Leibniz’s writings, which reveal his underlying assumptions on unity.

Descartes intended to revolutionize seventeenth-century philosophy and science. But first he had to persuade his contemporaries of the truth of his ideas. Of all his publications, Meditations on First Philosophy is methodologically the most ingenuous. Its goal is to provoke readers, even recalcitrant ones, to discover the principles of “first philosophy.” The means to its goal is a reconfiguration of traditional methodological strategies. The aim of this chapter is to display the methodological strategy of the Meditations. The text’s method is more subtle and more philosophically significant than has generally been appreciated. Descartes’ most famous work is best understood as a response to four somewhat separate philosophical concerns extant in the seventeenth century. Section 1 describes these. Section 2 discusses how Descartes uses and transforms them. A clearer sense of the Meditations’ methodological strategy provides a better understanding of exactly how Descartes intended to revolutionize seventeenth-century thought.