Translation for this volume by Lydia Patton of Chapter 9 (pages 179-200) of Émilie du Châtelet's Institutions de Physique (Foundations of Physics). Original publication date 1750. Paris: Chez Prault Fils.

If the allusive stratagems can claim to define a new type of systematicity, it is because they give access to a space where the singularity, the diagram and the metaphor may interlace, to penetrate further into the physico-mathematic intuition and the discipline of the gestures which precede and accompany ‘formalisation’. This interlacing is an operation where each component backs up the others: without the diagram, the metaphor would only be a short-lived fulguration because it would be unable to operate: without (...) the metaphor, the diagram would only be a frozen icon, unable to jump over its bold features which represent the images of an already acquired knowledge; without the subversion of the functional by the singular, nothing would come to oppose the force of habit. (shrink)

For Émilie Du Châtelet, I argue, a central role of the principle of sufficient reason is to discriminate between better and worse explanations. Her principle of sufficient reason does not play this role for just any conceivable intellect: it specifically enables understanding for minds like ours. She develops this idea in terms of two criteria for the success of our explanations: “understanding how” and “understanding why.” These criteria can respectively be connected to the determinateness and contrastivity of explanations. The crucial (...) role Du Châtelet’s principle of sufficient reason plays in identifying good explanations is often overlooked in the literature, or else run together with questions about the justification and likelihood of explanations. An auxiliary goal of the article is to situate Du Châtelet’s principle of sufficient reason with respect to some of the general epistemological and metaphysical commitments of her Institutions de Physique, clarifying how it fits into the broader project of that work. (shrink)

I show that unlike her rationalist predecessor Leibniz, Du Châtelet is committed to epistemic causal idealism about natural causes. According to this view, it is constitutive of natural causes that they are in principle knowable by us (i.e., finite intelligent beings). Du Châtelet’s causal idealism stems at least in part from the distinctive theoretical role played by the Principle of Sufficient Reason in her system (as presented in her _Institutions de physique_), as well as her argument for the Principle of (...) Sufficient Reason. I show that far from merely explicating Leibniz’s metaphysics, Du Châtelet develops a radical and novel rationalism that is in keeping with her core commitment to science. (shrink)

- Emilie du Châtelet offers an interesting and unusual account of the origin of our representation of extension. - She is an idealist about the essence extension, bodies and space, regarding them as mental constructs. - Du Châtelet's account requires a brute fact about the mind, in apparent tension with the Principle of Sufficient Reason.

This paper explores the theory of freedom that Emilie du Châtelet advances in her essay “On Freedom.” Using contemporary terminology, we can characterize this theory as a version of agent-causal compatibilism. More specifically, the theory has the following elements: (a) freedom consists in the power to act in accordance with one’s choices, (b) freedom requires the ability to suspend desires and master passions, (c) freedom requires a power of self-motion in the agent, and (d) freedom is compatible with moral necessity (...) but not with physical necessity. While these elements may at first appear disparate, the paper shows that they fit together quite well. The resulting theory is a surprising combination of doctrines that appear to be based on Samuel Clarke’s libertarian account of free will and doctrines that are reminiscent of the compatibilist accounts of John Locke, Anthony Collins, Gottfried Leibniz, and Thomas Hobbes. (shrink)

There is a tension in Emilie Du Châtelet’s thought on mathematics. The objects of mathematics are ideal or fictional entities; nevertheless, mathematics is presented as indispensable for an account of the physical world. After outlining Du Châtelet’s position, and showing how she departs from Christian Wolff’s pessimism about Newtonian mathematical physics, I show that the tension in her position is only apparent. Du Châtelet has a worked-out defense of the explanatory and epistemic need for mathematical objects, consistent with their metaphysical (...) nonfundamentality. I conclude by sketching how Du Châtelet’s conception of mathematical indispensability differs interestingly from many contemporary approaches. (shrink)

In this chapter, I examine similarities and divergences between Du Châtelet and Descartes on their endorsement of the use of hypotheses in science, using the work of Condillac to locate them in his scheme of systematizers. I conclude that, while Du Châtelet is still clearly a natural philosopher, as opposed to modern scientist, her conception of hypotheses is considerably more modern than is Descartes’, a difference that finds its roots in their divergence on the nature of first principles.

Leibniz endorses the world apart doctrine, according to which a substance is that which is independent of all other things except God. However, I will argue that in what appears to be a radical departure from the causal version of the world apart doctrine, Du Châtelet—whose metaphysics appears to be Leibnizian from a distance—embraces the causal connectedness of created substances. I further show that Du Châtelet’s rejection of Leibniz’s claim that a substance is causally independent of all other created substances (...) can be traced back to a more fundamental antiLeibnizian commitment on Du Châtelet’s part concerning the in-principle accessibility of natural (i.e., non-divine) sufficient reasons by finite minds and to her commitment to a causal theory of intentionality. (shrink)

There is a growing consensus that Emilie Du Châtelet’s challenging essay “On Freedom” defends compatibilism. I offer an alternative, libertarian reading of the essay. I lay out the prima facie textual evidence for such a reading. I also explain how apparently compatibilist remarks in “On Freedom” can be read as aspects of a sophisticated type of libertarianism that rejects blind or arbitrary choice. To this end, I consider the historical context of Du Châtelet’s essay, and especially the dialectic between various (...) strands of eighteenth-century libertarianism and compatibilism. (shrink)

This projecrt aims to present an online Reading Guide to help students, teachers and researchers navigate through Du Châtelet’s Foundations of Physics, or Institutions de physique (1740/42) and to make this important text visible to a broad audience.

I examine Du Châtelet’s methodology for physics and metaphysics through the lens of her engagement with Newton’s Rules for Reasoning in Natural Philosophy. I first show that her early manuscript writings discuss and endorse these Rules. Then, I argue that her famous published account of hypotheses continues to invoke close analogues of Rules 3 and 4, despite various developments in her position. Once relevant experimental evidence and some basic constraints are met, it is legitimate to inductively generalize from observations; general (...) hypotheses can thereafter be assumed as true until contrary experiments show otherwise. I conclude by arguing that this account of induction plays an essential role in her metaphysics, both in an argument for simple substances—which has an inductive premise—and in her attempt to distinguish acceptable and unacceptable metaphysical commitments. (shrink)

Much early modern metaphysics grew with an eye to the new science of its time, but few figures took it as seriously as Emilie du Châtelet. Happily, her oeuvre is now attracting close, renewed attention, and so the time is ripe for looking into her metaphysical foundation for empirical theory. Accordingly, I move here to do just that. I establish two conclusions. First, du Châtelet's basic metaphysics is a robust realism. Idealist strands, while they exist, are confined to non-basic regimes. (...) Second, her substance realism seems internally coherent, so her foundational project appears successful.I have two aims in this paper. Historically, I show that du Châtelet's main source of inspiration was Christian... (shrink)

In this chapter, we argue that Du Châtelet’s account of motion is an important contribution to the history of the absolute versus relative motion debate. The arguments we lay out have two main strands. First, we clarify Du Châtelet’s threefold taxonomy of motion, using Musschenbroek as a useful Newtonian foil and showing that the terminological affinity between the two is only apparent. Then, we assess Du Châtelet’s account in light of the conceptual, epistemological, and ontological challenges posed by Newton to (...) any relational theory of motion. What we find is that, although Du Châtelet does not meet all the challenges to their full extent, her account of motion is adequate for the goal of the Principia: determining the true motions in our planetary system. (shrink)

In the second chapter of her <i>Institutions de Physique</i> Emilie Du Chatelet gives two cosmological arguments for the existence of God. In this chapter I focus on the first of these arguments. I argue that, while it bears some significant similarities to arguments given by John Locke and Christian Wolff, it improves on these arguments in at least two ways. First, it avoids a potential equivocation in Locke's argument; and second, it avoids Wolff's mere stipulation that whoever claims that (...) there cannot be an infinite regress of contingent beings does not understand what a sufficient reason is. I finally argue that her argument avoids a related objection, considered by David Hume, on which to explain a causal chain is merely to explain each link in the chain. (shrink)

I argue for two main points in historiography of physics regarding the significance of Du Châtelet's Foundations of Physics in the development of mechanics. The first is that, despite Du Châtelet calling it a textbook in the Preface, it should not be understood as 'merely' a textbook. Instead, it fits in a tradition of women involved in natural philosophy in that era using liminal publication opportunities, and to reduce some of the resistance to their publication. Even these liminal opportunities were (...) rare and mostly available to women of very high social standing and wealth, who also happened to have supportive families or spouses, and were usually associated with some other well-known male thinker. The second point is that, even if we treat Foundations as a textbook, the way in which it synthesizes and refines work by Newton, Leibniz, Descartes, and others, meets the criteria given by Kuhn for the establishment of a first paradigm, which is not complete without such a definitive statement that enables the mop-up work characteristic of normal science. I conclude that by Kuhn's own criteria, he ought to have identified Du Châtelet as a key part of establishing the first paradigm in physics. She blazed a trail for others to follow. (shrink)

I begin by outlining Du Châtelet’s ontology of mathematical objects: she is an idealist, and mathematical objects are fictions dependent on acts of abstraction. Next, I consider how this idealism can be reconciled with her endorsement of necessary truths in mathematics, which are grounded in essences that we do not create. Finally, I discuss how mathematics and physics relate within Du Châtelet’s idealism. Because the primary objects of physics are partly grounded in the same kinds of acts as yield mathematical (...) objects, she thinks we are sometimes licensed in drawing conclusions about physical things from mathematical premises. (shrink)

This paper examines Du Châtelet’s and Kant’s responses to the famous vis viva controversy – Du Châtelet in her Institutions Physiques (1742) and Kant in his debut, the Thoughts on the True Estimation of Living Forces (1746–49). The Institutions was not only a highly influential contribution to the vis viva controversy, but also a pioneering attempt to integrate Leibnizian metaphysics and Newtonian physics. The young Kant’s evident knowledge of this work has led some to speculate about his indebtedness to her (...) philosophy. My study corrects such speculations as well as misunderstandings of the Living Forces. This corrective result has implications for how to investigate Kant’s relation to the ever-evolving landscape of Leibniz exegeses. (shrink)

To provide metaphysical grounds for the physics of her time, Du Châtelet argued for the notion of an active force. This was different from the impressed force in Newton’s second law. The former force was a property of a body, whereas the latter was an external cause. I shall study this discrepancy and argue that the interactive concept of force in Newton’s third law is consistent with Du Châtelet’s standards for an intelligible physics. Consequently, the interaction entailed by the law (...) of universal gravitation complies with Du Châtelet’s principles of human knowledge. (shrink)

Summary In about 1735, Emilie Du Châtelet began to translate Mandeville's Fable of the Bees. Her work, which is largely ignored by scholars, did, as this article demonstrates, turn out to be one of transformation rather than of translation and came at a crucial moment in the emerging French luxury debate. So far commercial society and luxury had been defended in purely economic terms, for instance in Melon's Essai politique, or as an aspect of divine providence for fallen man, by (...) Pierre Nicole amongst others. There was as yet no coherent defence on the level of secular ethics. As this article shows, Du Châtelet set out to remedy this. In co-operation with Voltaire, with whose recent praise of English society in the Lettres philosophiques she strongly identified, she rewrote the Fable to offer a defence of modern commercial society as both natural and moral. The article argues that she was able to do so by taking recourse to classic Epicureanism in the guise of Lucretius' De rerum natura, as an alternative to the Neo-Epicureanism, with its Augustinian overtones, as espoused by Mandeville. Voltaire in turn used her translation to lay the foundations for his defence of commercial society and progress in his Traité de métaphysique in which he uses the precise passages she had inserted into Mandeville's original. This article analyses the further aspects Voltaire adds to her arguments. Taken together, Du Châtelet's ?translation? and Voltaire's Traité offer a coherent defence of bourgeois society that would underlie Voltaire's later historiographical and philosophical works and which were crucial to his concept of ?Enlightenment? and ?progress? (shrink)

Du Châtelet holds that mathematical representations play an explanatory role in natural science. Moreover, she writes that things proceed in nature as they do in geometry. How should we square these assertions with Du Châtelet’s idealism about mathematical objects, on which they are ‘fictions’ dependent on acts of abstraction? The question is especially pressing because some of her important interlocutors (Wolff, Maupertuis, and Voltaire) denied that mathematics informs us about the properties of material things. After situating Du Châtelet in this (...) debate, this chapter argues, first, that her account of the origins of mathematical objects is less subjectivist than it might seem. Mathematical objects are non-arbitrary, public entities. While mathematical objects are partly mind-dependent, so are material things. Mathematical objects can approximate the material. Second, it is argued that this moderate metaphysical position underlies Du Châtelet’s persistent claims that mathematics is required for certain kinds of general knowledge, including in natural science. The chapter concludes with an illustrative example: an analysis of Du Châtelet’s argument that matter is continuous. A key premise in the argument is that mathematical representations and material nature correspond. (shrink)

A survey article on the metaphysics, physics and methodology of Du Châtelet.

In her Discourse on Happiness, Émilie du Châtelet argues susceptibility to illusion is one of the five ‘great machines of happiness,’ and that ‘we owe most of our pleasures to illusions’. However, many who read the Discourse find this aspect of her view puzzling and in tension with her claims that we must always seek truth and obey reason. To understand better her claims in the Discourse on Happiness, this article explores Du Châtelet's discussions of illusions in her Foundations of (...) Physics, On Liberty, and the Dissertation on the Nature and Propagation of Fire. I distinguish four types of illusions that Du Châtelet posits and clarify the ways in which these relate to her views on happiness and love in the Discourse and argue that she avoids deceptive or perpetual illusions of happiness through the use of the principle of sufficient reason. (shrink)

Im Mittelpunkt der vorliegenden Studie steht die Frage nach der Tragweite und Anwendungsrelevanz der Methodenlehre Émilie du Châtelets für die Physik im 18. Jahrhundert, mit der sich die Französin an der Diskussion um Energie- und Impulserhaltung und um das Prinzip der kleinsten Wirkung beteiligte. Andrea Reichenberger zeigt, dass Prinzipien und Hypothesen für Émilie du Châtelet als Fundament und Gerüst wissenschaftlicher Erkenntnis gelten. Im Zusammenspiel beider Komponenten erweisen sich das Prinzip des Widerspruchs und das Prinzip des zureichenden Grundes als regulative Leitlinien (...) und Handlungsmaxime für die auf Hypothesen gestützte Theoriebildung und -begründung. Die sich daraus ergebenden Konsequenzen für den Status und Inhalt der Newtonschen Axiome werden exemplarisch aufgezeigt. (shrink)

I argue that Émilie Du Châtelet breaks with Christian Wolff regarding the scope and epistemological content of the principle of sufficient reason, despite his influence on her basic ontology and their agreement that the principle of sufficient reason has foundational importance. These differences have decisive consequences for the ways in which Du Châtelet and Wolff conceive of science.

This paper discusses the contribution of Madame Du Châtelet to the reception of Newtonianism in France prior to her translation of Newton’s Principia. It focuses on her Institutions de physique, a work normally considered for its contribution to the reception of Leibniz in France. By comparing the different editions of the Institutions, I argue that her interest in Newton antedated her interest in Leibniz, and that she did not see Leibniz’s metaphysics as incompatible with Newtonian science. Her Newtonianism can be (...) seen to be in the course of development between 1738 and 1742 and it was shaped by contemporary French debates and the achievement of French Newtonians like Maupertuis in confirming his theories. Her Institutions therefore is linked to the same drive to disseminate Newtonianism undertaken by popularisations such as Voltaire’s Elements de la philosophie de Newton and Algarotti’s Newtonianismo per le dame.Author Keywords: Emilie du Châtelet; Isaac Newton; Voltaire; French reception of Newtonianism. (shrink)

Émilie Du Châtelet’s Foundations of Physics (Institutions de physique, 1740/42) has recently been attracting increasing interest from analytical philosophy in the anglophone world. Du Châtelet’s conception of space and time constitutes a controversial issue. I argue that the current debate underestimates the modal approach and epistemological turn in Du Châtelet’s view on space and time. A historical perspective on Abraham Gotthelf Kästner’s criticism and Jean Henry Samuel Formey’s plagiarism of Du Châtelet underlines the significance of this turning point. Against this (...) background, I revisit Leonhard Euler’s space-time realism and its influence on Immanuel Kant. -/- Les Institutions de physique (1740/1742) d’Émilie Du Châtelet suscitent depuis peu un intérêt croissant dans le monde anglophone, chez les philosophes analytiques. Une question controversée concerne les concepts d’espace et de temps de Du Châtelet. Je soutiens que le débat actuel sous-estime l’approche modale et la tournure épistémologique des considérations de Du Châtelet sur l’espace et le temps. Un regard historique sur la critique d’Abraham Gotthelf Kästner et le plagiat de Du Châtelet par Jean Henry Samuel Formey souligne l’importance de ce tournant. Dans ce contexte, je revisite le réalisme spatio-temporel de Leonhard Euler et son influence sur Emmanuel Kant. (shrink)

Many commentators have suggested that the metaphysical portions of Emilie du Châtelet's Institutions de physique are a mere retelling of Leibniz's views. I argue that a close reading of the text shows that du Châtelet's cosmological argument and discussion of God's nature contains both Lockean and Leibnizian elements. I discuss where she follows Locke in her arguments, what Leibnizian elements she brings in, and how this enables her to avoid some of the mistakes commonly attributed to Locke's formulation of the (...) cosmological argument. I show that while du Châtelet accepts the causal principle ex nihilo nihil fit, she does not utilize Locke's stronger causal principle. I also discuss her use of the principle of sufficient reason in both improving the Lockean cosmological argument and in proving the attributes of God. (shrink)

Much scholarship has claimed the physics of Emilie du Châtelet’s treatise, Institutions de physique, is Newtonian. I argue against that idea. To do so, I distinguish three strands of meaning for the category ‘Newtonian science,’ and I examine her book against them. I conclude that her physics is not Newtonian in any useful or informative sense. To capture what is specific about it, we need better interpretive categories.

In diesem Band werden neueste Forschungen zur Physikerin, Mathematikerin und Philosophin Emilie Du Châtelet vorgestellt. Emilie Du Châtelet genoss in der deutschen Aufklärung eine hohe Reputation. Sie verband Leibniz Metaphysik mit der Physik von Newton und gelangte zu erstaunlichen Ergebnissen, die die Physik auf den Weg zu Einsteins Energieformel führte. Ihre Werke wurden sofort ins Deutsche übersetzt, Kant nimmt in seiner ersten Dissertation von 1747 auf sie Bezug. Die Sammlung stellt Texte vor, die den Einfluss der deutschen Aufklärung auf Du (...) Châtelets und Du Châtelets Einfluss auf die deutsche Philosophie diskutieren. Die großen Namen der Epoche stehen hier zur Debatte, Leibniz, Wolff, Boskovic, Euler, Friedrich II, Voltaire, La Mettrie und viele weitere Größen der Aufklärung werden in ihrem Zusammenhang mit Du Châtelet vorgestellt. (shrink)

In lieu of an abstract, see the following excerpt: -/- Though his work has until now gone untranslated and been largely ignored in English scholarship, the historian of philosophy François Châtelet played a major role in the development of French thought that is on par with that of his more well-known contemporaries. Born in 1925, Châtelet was founding member of the University of Vincennes, Paris VIII’s experimental department of philosophy alongside Michel Foucault in the aftermath of the 1968 student protests. (...) In 1983, he would establish the Collège Internationale de Philosophie in Paris along with other prominent philosophers, an institution that in Alessandra Campana’s words, is at “the forefront of militant and engaged critical thinking,” in which it has sought to “relocate philosophy at the intersection of science, politics, psychoanalysis, art and literature, jurisprudence, and economy.” Châtelet’s association with radical educational institutions and the interdisciplinarity of research undertaken at the latter both point to what can be understood to be the essence of his philosophical project: that the history of philosophy is also a politics of philosophy. La Grèce Classique, La Raison, L’État, which was first published in 1978 and appears here in translation for the first time under the title Classical Greece, Reason, and the State, is exemplary in this regard, providing a powerful critique of the history of philosophy and its purported Greek origins. As Deleuze argues, Châtelet reveals that “Athens was not the advent of an eternal reason, but the singular event of a provisional rationalisation. In this view, the essence of classical philosophy cannot be extended to the contemporary era—neither in its original form, or in a revised form that has been modified and updated across the passage of time. Therefore, by politicising philosophy and its history, Châtelet’s work also shows philosophy to be indicative of a particular cultural moment, rather than as an the state, philosophy, and the tyranny of the logos · isolated discipline cut off from the influences of material life. He establishes a form of ‘rational empiricism’ for conducting a history of political philosophy that rejects universality for potentiality. Said otherwise, his work is indicative of what might be called the poststructuralist critique of historical narrative surrounding the canon of western thought, a critique that Michael Hardt rightfully argues “has problematised the foundations of philosophical and political thought.” However, Châtelet has made important contributions to the poststructuralist approach to theorising the western tradition that remain novel and insightful to a contemporary audience, rather than simply being one of many to problematise philosophy’s purported foundations. (shrink)

In the mid-eighteenth century, it was usually taken for granted that all curves described by a single mathematical function were continuous, which meant that they had a shape without bends and a well-defined derivative. In this paper I discuss arguments for this claim made by two authors, Emilie du Châtelet and Roger Boscovich. I show that according to them, the claim follows from the law of continuity, which also applies to natural processes, so that natural processes and mathematical functions have (...) a shared characteristic of being continuous. However, there were certain problems with their argument, and they had to deal with a counterexample, namely a mathematical function that seemed to describe a discontinuous curve. (shrink)

Andrew Janiak has recently claimed that Mme Du Châtelet was “the Enlightenment's most dangerous woman.” There is no evidence that contemporaries regarded her as dangerous. There is no evidence that contemporaries (publishing in French, in France, during her lifetime) took exception to a woman philosopher, or regarded her epistemology as innovative and/or subversive. The claim that she was dangerous is thus a peculiar one, as it is unsupported by any empirical evidence. A consideration of the various meanings of the word (...) “dangerous” leads to the conclusion that Du Châtelet was not a threat to the culture of the French Enlightenment. (shrink)

In the Metaphysical Foundations of Natural Science, Kant attempts to argue a priori from the indefinite divisibility of space to the indefinite metaphysical divisibility of matter. This is one type of argument from the continuity of space—purportedly established by Euclidean geometry—to the continuity of matter. I compare Kant's argument to parallel reasoning in Du Châtelet, whose work he knew. Both philosophers appeal to idealism about matter in their reasoning, yet also face difficulties in explaining why continuity, though not some other (...) properties from geometry, applies to matter. Both also risk inconsistency in adopting potentialist accounts of material parts, while also committing to realism about infinitesimals. An important difference between them is that Du Châtelet deploys at least three definitions of continuity; only one of these, amounting to indefinite divisibility, is shared with Kant. (shrink)

This article discusses Du Châtelet’s challenging claim that entertaining illusions, especially illusions of being esteemed by posterity, is conducive to happiness. It does so by taking a contextualizing approach, contrasting her views with some Epicurean aspects of the views on illusions and happiness in Bernard de Fontenelle and Julien Offray de La Mettrie. I will argue for three claims: (1) Du Châtelet’s comparison between self-related illusions and illusions in the theater is vulnerable to objections deriving from some distinctions that Fontenelle’s (...) poetics draws between the role of illusions in the theater and the role of illusions in real life. (2) Examining Fontenelle’s analysis of the detrimental effects of self-related illusions indicates several respects in which Du Châtelet has underestimated the ambivalent nature of illusions. (3) Du Châtelet’s view that illusions are akin to sensations that are favorable to us problematically generalizes La Mettrie’s insight that some acts of the imagination have a quasi-perceptual nature. (shrink)

This article discusses Du Châtelet’s challenging claim that entertaining illusions, especially illusions of being esteemed by posterity, is conducive to happiness. It does so by taking a contextualizing approach, contrasting her views with some Epicurean aspects of the views on illusions and happiness in Bernard de Fontenelle and Julien Offray de La Mettrie. I will argue for three claims: (1) Du Châtelet’s comparison between self-related illusions and illusions in the theater is vulnerable to objections deriving from some distinctions that Fontenelle’s (...) poetics draws between the role of illusions in the theater and the role of illusions in real life. (2) Examining Fontenelle’s analysis of the detrimental effects of self-related illusions indicates several respects in which Du Châtelet has underestimated the ambivalent nature of illusions. (3) Du Châtelet’s view that illusions are akin to sensations that are favorable to us problematically generalizes La Mettrie’s insight that some acts of the imagination have a quasi-perceptual nature. (shrink)

British Journal for the History of Philosophy, Volume 21, Issue 1, Page 207-209, January 2013.

I distinguish three ways in which early modern rationalists seek to apply the principle of sufficient reason to empirical science, and critically assess some of their attempts to do so. I focus especially on how these thinkers assume substantive theories of explanation and intelligibility--which are indebted to the mechanist and experimentalist traditions--in many of their deployments of this rationalist principle. A recurring problem is that these philosophers deploy their standards of intelligibility inconsistently: some of their own favored explanations do not (...) always live up to their standards. I argue that the problem is especially acute for Leibniz and Euler, given their enthusiasm for final-causal explanations. (shrink)