Descartes’ work on optics spanned his entire career and represents a fascinating area of inquiry from both the perspectives of the history of science and his systematic natural philosophy. This entry offers a brief account of Descartes' seminal work in optics, the Dioptrique, often translated as the Optics or, more literally, as the Dioptrics.
Descartes’ work on optics spanned his entire career and represents a fascinating area of inquiry from both the perspectives of the history of science and his systematic natural philosophy. This entry offers an overview of Descartes’ understanding of light, his derivations of the two central laws of geometrical optics, and a sampling of the optical phenomena he sought to explain.
This entry - originally published in 2007, substantially updated in 2014 - provides 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 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.
This essay offers an alternative account of Leibniz’s views on substance and fundamental ontology. The proposal is driven by three main ideas. First, that Leibniz’s treatment should be understood against the backdrop of a traditional dispute over the paradigmatic nature substance as well as his own overarching conciliatory ambitions. Second, that Leibniz’s metaphysics is intended to support his conciliatory view that both traditional views of substance are tenable in at least their positive and philosophical respects. Third, that the relationship between immaterial substances, corporeal substances, and ordinary bodies in Leibniz’s metaphysics is best understood as one of “material” constitution. The interpretation as a whole thus suggests that Leibniz needn’t be read as offering either an exclusive defense of corporeal substance realism, nor of immaterial substance idealism, nor as being deeply torn (at a time or over time) between two such views. He may instead be seen as offering a carefully presented, consistent, and sophisticated conciliatory account of substance.
This paper argues that the standard reckoning of early modern proponents and opponents of traditional teleology tracks something deep and important in the period’s shifting attitudes towards teleology and teleological explanations. The first main section identifies two central commitments of ancient and medieval views on teleology. The second section argues that mainstream later medieval and early modern philosophers opposed the teleology of their predecessors by denying the explanatory parity of teleological and efficient causal explanations. The third section argues that Spinoza’s rejection of traditional teleology is rooted in his rejection of the ancient and medieval view that objective goodness is explanatory. Finally, the last main section argues that Leibniz’s claim to being a champion of traditional teleology rests securely on his attempt to defend both the traditional theses of explanatory parity and of explanatory goodness.
Confronting the threat of a Spinozistic necessitarianism, Leibniz insists that not all possible substances are compossible – that they can’t all be instantiated together – and thus that not all possible worlds are compossible – that they can’t all be instantiated together. While it is easy to appreciate Leibniz’s reasons for embracing this view, it has proven difficult to see how his doctrine of incompossibility might be reconciled with the broader commitments of his larger philosophical system. This essay develops, in four sections, a novel solution to the “puzzle of incompossibility.” The first section frames the difficulty more carefully and briefly argues that the two dominant strategies developed by Leibniz’s commentators fail to solve it fully insofar as they require simply abandoning one or another of its motivating commitments. The second and third sections show how Leibniz’s guiding analogy of a geometrical packing or tiling problem may be applied to solve the puzzle of incompossibility in the context of finite and infinite worlds composed of extended corporeal substances. Finally, the fourth section shows how the strategy of Leibniz’s packing analogy might be applied even in the context of a thoroughly idealist metaphysics in which the only true substances are non-extended, mind-like “monads.” The essay concludes by drawing some connections between Leibniz’s thinking about the puzzle of incompossibility and the development of his views concerning the status of corporeal substances and extended bodies.
It has been tempting to suppose that the central theses of Leibniz's mature understanding of the laws of nature are forged in the domain of physics and opportunistically carried over to the domain of optics. This essay argues that that tempting story gets things essentially the wrong way around. Each of its three main sections accordingly takes up one of the defining features of Leibniz’s mature understanding of the laws of nature and argues that it is best understood as arising from his increasingly sophisticated attempts to show that the laws of optics can be thought of as selecting one uniquely determined actual path from an infinite family of possible paths. Collectively the three sections aim to show that the crucial nexus of views at the heart of Leibniz’s mature philosophical understanding of the laws of nature has its most intelligible roots in his optical derivations, which appear to have paved the way – both historically and conceptually – for the philosophical significance he assigns to his discoveries in the domain of physics. Optics the horse, as it were, physics the cart.
This essay examines one of the cornerstones of Leibniz’s defense of teleology within the order of nature, namely, his derivation of the two central laws of geometrical optics from his “Most Determined Path Principle” or “MDPP”. The first section places the MDPP in its historical context, and argues that it allows Leibniz to bring to the fore philosophical issues concerning the legitimacy of teleological explanations by addressing two technical objections raised by Cartesians to non-mechanistic derivations of the laws of optics. The second section argues that, by drawing on laws such as the MDPP, Leibniz is able to introduce a thin notion of teleology that gives him the resources to respond to the most pressing charges of his day by showing how teleology within the order of nature may be stripped of problematic Scholastic commitments, fitted to accepted explanatory structures, and successfully applied to a wide and promising range of natural phenomena. Finally, the third section argues that contemporary philosophers have been overly hasty in their dismissal of Leibniz’s account of natural teleology, and indeed that their own generally thin conceptions of teleology have left them with few well-motivated resources for resisting Leibniz’s elegant position.
Berkeley ’s commentators have been highly critical of his account of human agency. In this essay I argue that there is a rather straightforward reading of his view that is historically sensitive, philosophically well-motivated, and fits squarely with his texts. The paper falls into four main sections. The first section briefly revisits three options concerning the relationship between human and divine agency available to theistically minded philosophers in the medieval and early modern eras. The second argues that of those three views only the position of concurrentism is consistent with Berkeley’s texts. The third section explores Berkeley’s reasons for adopting concurrentism, especially as opposed to occasionalism, by highlighting three motivating considerations drawn from his larger philosophical system. Finally the fourth section attempts to flesh out Berkeley’s understanding of human activity by looking at how we might understand his claim that we move our legs ourselves in light of his commitments to idealism and concurrentism.
In his attempt to reconcile piety and the new science, teleology and mechanism, final causation and efficient causation, Leibniz often speaks of there being two realms – a “kingdom of power or efficient causes” and “a kingdom of wisdom or final causes.” In this essay, I explore Leibniz’s attempt to apply this doctrine to the natural world. The essay falls into four main parts. The first part looks to Leibniz’s much neglected work in optics for the roots of his view that the world can be seen as being governed by two complete sets of equipotent laws. The second offers an account of how this picture of lawful over-determination is to be reconciled with Leibniz’s mature metaphysics. The third addresses a line of objection proposed by David Hirschmann to the effect that Leibniz’s two realms doctrine as applied to the physical world undermines his stated commitment to an efficient, broadly mechanical, account of the natural world. Finally the fourth part suggests that Leibniz’s thinking about the harmony of final and efficient causes in connection with corporeal nature may help to shed light on his understanding of the teleological unfolding of monads as well.