Since the time of Berkeley, a predominant interpretation of Descartes' theory of vision is that it begins with a bare sensation in two-dimensions, with the third dimension being inferred by unnoticed or habitual processes of reasoning. There have been various challenges to this view, including my own recent argument that, in the Treatise on Man, Descartes developed a sophisticated account of a physiological mechanism to "compute" the results of what he terms "natural geometry." Accordingly, the triangle of convergence (involving the two eyes focused on a distant point) does not involve mental computation but physiomechanical computation. Without attributing representations to the bodily states, he treats them as informational in a Gibsonian sense: certain bodily states are correlated with distal states of affairs, and they produce in the mind a representation of that state of affairs-in this case, of a location in space at a distance. Thus, in at least some cases, depth and distance are phenomenally immediate sensory representations and not the product of mental inference. In this talk, I will extend this sort of account to other areas of Descartes' theory of visual perception, including the perception of colors in bodies and of the potential benefits and harms of external objects. Drawing on the Treatise and the Passions, I will suggest that Descartes envisioned, in these cases, brain states that correlate with external states of affairs such as physical color in bodies and potentially beneficial or harmful properties of bodies, and that these brain states then cause mental representations of surface colors, things that are edible, dangerous animals, and the like.

The status of the Laws of Nature in the Leviathan has been a puzzle for Hobbes scholars. According to one recent view, called the "definitional" view, the Laws of Nature arise as edicts that follow from the command of reason alone, and it is reason that enables humans to escape from the state of nature. Such a view relies upon two widely-held assumptions about Hobbes's project: first, that it was "scientific" because it was modeled upon a type of geometrical demonstration that began with axioms, such the definition of a law of nature in Leviathan XIV, and proceeded by deduction to demonstrate the remaining Laws of Nature; and second, that it was grounded in a conception of reason as being in conflict with the passions.
    My goal in this paper is to reorient scholarship on Hobbes's politics with respect to the first widely-held assumption by providing a new way of understanding the politics as a science. I argue that Hobbes's physics sheds light on this issue. Specifically, instead of deduction in an axiomatic system, I show that "geometrical" in this context means that one learns causal principles by engaging in a construction beginning with simple bodies and motions. This form of construction grounds geometry in a thought experiment in De corpore (On Body) and provides scientific knowledge of the motions of natural bodies; in the state of nature thought experiment, this form of construction provides scientific knowledge of the passions as the only motions responsible for human action. I conclude by briefly showing how this relates to debates about Hobbes's understanding of reason and the passions.

In "The Problem of the Criterion," Roderick Chisholm argued that Spinoza was an epistemic Particularist. By this, Chisholm meant that Spinoza thought that philosophical enquiry begins with what is already known. Chisholm contrasts the Particularism he read into Spinoza, with the Methodism he read into Descartes, who, according to Chisholm, began his philosophical enquiry with a method that allowed him to distinguish cases of knowledge from cases of mere belief. Today, Spinoza is commonly read as an epistemic Metaphysicalist, that is, as a philosopher who derives his epistemology from a metaphysical theory. In this paper, I argue that Spinoza is, in fact, properly read as a sort of Cartesian Methodist-I argue that Spinoza constructs his philosophy from a method of certainty.

Existing accounts of Spinoza's doctrine of intuitive knowledge (scientia intuitiva) characterize it as knowledge that proceeds from adequate cognition of God's essence to an adequate cognition of a given mode's unique formal essence. On such accounts, intuitive knowledge is at-a-glance knowledge of a lot. After all, if the essence is conceived as a perfectly individuated effect, and if this sort of knowledge proceeds from God to God's effects, then it seems the individuating causes—lots and lots of modes and infinite modes—are going to be understood too. If this is what intuitive knowledge is, then it seems to be very rare indeed.
    I will argue that while attaining intuitive knowledge (and enjoying the beatitudo that comes with it) is still rather difficult, what it gives us is not apprehension of so many details. Rather, intuitive knowledge is adequate and true knowledge of a fundamental causal structure that reason, the second kind of knowledge, misses. While reason is adequate and true knowledge of how things considered sub specie aeternitatis are situated in a causal nexus of necessary laws and causes, it is not knowledge that all the formal essences it comprehends are modes inhering in and necessarily caused by the one necessarily existing eternal substance.
    This monist, necessitarian insight does seem like it can come in a flash. In fact, I think we can detect in the Ethics a trace of the ontological proof in Descartes' Fifth Meditation, a proof the conclusion of which Descartes insists is seen immediately and self-evidently—that is, intuitively. Descartes' proof starts from an idea (the idea of God's essence) with a given, immediately discernible content (necessary existence). A reflective and careful enough meditator will see that she has such an idea and will immediately see that God necessarily exists. It seems the intuition of scientia intuitiva is very much like the intuition in the ontological proof. Spinoza insists that "the human mind has an adequate cognition of God's eternal and infinite essence [mens humana adaequatam habet cognitionem aeternae et infinitae essentiae Dei]" (2p47). While Descartes thinks that there is just one special idea that contains necessary existence, Spinoza is going to insist that any idea contains necessary existence; any cognition will involve cognition of an attribute of God. Yet not all thinkers, and not even all thinkers who are adept at reasoning sub specie aeternitatis, will recognize what they have (it seems most thinkers will need to read the Ethics first). But once a thinker does see that she has a cognition of God's eternal and infinite essence, it will be immediately self-evident that what she reasons about sub specie aeternitatis are in fact modes inhering in and necessarily caused by the one necessarily existing eternal substance. Her knowledge of the second kind enables her to see that things are necessitated given other things, but now she has the intuitive, adequate, and true knowledge that anything and everything—and whatever her particular idea is of—exists with absolute necessity.
    Such intuitive knowledge might not come easily, but if this is what it is, it is at least knowledge that many people could plausibly have. All the better for our prospects for beatitudo!

When J.M.E. McTaggart put Spinoza on his short-list of philosophers who regard time as unreal, he fell in line with a reading of Spinoza's philosophy of time advanced by contemporaneous British Idealists and by Hegel. In Faith and Knowledge, for example, Hegel comments that "every line of Spinoza's system makes the proposition that time and succession are mere appearances so utterly trivial that not the slightest trace of novelty and paradox is to be seen in it." The idealists understood that there is much at stake concerning the ontological status of Spinozistic time. If time is essential to motion—as Spinoza's physical writings make clear—then temporal idealism entails that nearly everything, apart from God conceived sub specie aeternitatis, is imaginary. In the first part of the paper, I argue that although time is indeed "imaginary"—in a sense "no one doubts" as Spinoza says—there is no good reason to infer that finite bodies, the infinite modes, and conatus are imaginary in the same sense. To avoid this conflation, we need to follow Spinoza (who follows Descartes) in carefully distinguishing between tempus and duratio. Duration is not only real; it has all the structure needed to ground Spinozistic motion, bodies and conatus. In particular, it is inherently successive. This secures the mundane reality of modes while highlighting the unique and timeless being of God. In the second part of the paper, I examine Spinoza's reasons for relegating time to the imagination. While these reasons are shared by other prominent philosophers known to Spinoza, notably Descartes and Hobbes, in the case of Spinoza they betray a deep antagonism to certain "mathematization" projects of seventeenth century natural philosophy (in spite of Spinoza's own affection for the more geometrico). Drawing on work of Gueroult, Schmaltz, Melamed, and others, I consider the scientific and epistemological implications of Spinoza's opposition to the mathematization of time, space and motion.

As Leibniz said to Arnauld, “I hold this identical proposition, differentiated only by the emphasis, to be an axiom, namely, that what is not truly one being is not truly one being either.” The notions of being and unity are mutually supporting. I will try to shed light on Leibniz’s changing notions of substance and being by concentrating on his changing views about unity and the individual, from his early Bachelor’s thesis (Disputatio Metaphysica de Principio Individui, 1663), to his middle period treatise Discours de Métaphysique (1686). In the process, I also discuss Leibniz’s views about individuation in De Transubstantiatione (1668), Confessio Philosophi (1672-73?), Meditatio de Principio Individui (1676), some of his logical-grammatical texts (Definitiones: aliquid, nihil, 1679), Notationes generales (1683-85?), and his Notes on Cordemoy (Ex Cordemoii Tractatu de Corporis et Mentis Distinctione, 1685). I also try to relate Leibniz’s views with those of others, especially seventeenth-century Scholastics.

In the later version of the Confessio Philosophi (1677?) Leibniz offers his per se analysis of modality, treating necessary and contingent truths in terms of whether the reasons grounding the truth are internal or external to the essence or definitional concept of the subject of the truth. Highlighting the modal relevance of those features that follow from the essence of a subject alone is not Leibniz's philosophical innovation; arguably Spinoza's per se account influenced Leibniz. However, the implications of a per se analysis hinge on one's views of essence and definitional concepts, and Leibniz's treatment of these makes room for innovation relative to his predecessors. Unfortunately, the success of Leibniz's per se account in his early work rests on the stability of his notions of essence and definitional concept, which render an incomplete (at best) or untenable (at worst) account of modal claims by Leibniz's own standards.
    In the secondary literature the per se account of modality is sometimes championed as an important part of Leibniz's modal analysis in his later work as well as his early work. While I'm sympathetic to this interpretation, his later implementation of the per se account must be understood in light of the struggles in his early texts. I will explore the development of the per se account in his early work to detail the difficulties we should expect Leibniz to address if he is to adopt the per se view later on.

Most philosophers in the 17th & 18th century believe, rather plausibly, that the world contains a variety of bodies. However, there is a major challenge to this view arising from the commitment to the material plenum. Given the plenum, how can material things exist without one another? If material things cannot exist independently, is there really a plurality of things at all? Or, is the physical world a single, material substance? I call the problem indicated by these questions the Monist's Challenge. In this paper, I show the way in which Leibniz and Descartes are vulnerable to this challenge. I argue that Leibniz successfully responds to the Monist's Challenge by distinguishing between different types of dependence. On my interpretation of Leibniz's view, the material plenum involves only what I call generic dependence, which is compatible with the existence of a variety of bodies. I show that there is some basis for attributing this solution to Descartes as well, though Descartes does not engage the problem directly.

In this paper I argue that Newton's theory of space has the untenable consequence that God depends on space for his existence and is therefore not an independent being. The argument proceeds in stages. First, I show that Newton believed that space was a being and that God and space were ontologically distinct. Then I show that Newton believed that the existence of space was a necessary condition for the existence of any other being. Following this I discuss the ways in which this makes God depend on space for his existence and why this is unacceptable for traditional conceptions of God. Before concluding I offer two considerations on Newton's behalf that might ameliorate the difficulty.

There are two main points of disagreement with respect to Locke's discussion of human freedom in Book II, chapter xxi of An Essay Concerning Human Understanding (hereafter: Essay):
    (1) Whether Locke is a Hobbesian about free agency: if so, then on his view an agent is free just when she has the ability to do what she wills. If not, then Locke thinks that there is another aspect to human freedom that is fulfilled when an agent acts for a particular kind of good - "real Bliss" (cf. Essay II.xxi.63). (See Yaffe: 2000 for the latter view, and Rickless: 2001 for the former.)
    (2) Whether the power to suspend desire, introduced in the second edition of the Essay (II.xxi.47) ushers a kind of indeterminist freedom into his view thus creating a conflict with the volitional determinism elaborated and defended throughout the chapter (from the first edition to the last) as the explanation for physical and psychological change: if so, the power to suspend desire indicates that Locke holds that the human mind possesses the capacity to refrain from pursuing the thing for which it is most uneasy (or desirous) at a given moment (see Colman: 1952; Schouls: 1992; Chappell: 1994, 1998; Rickless: 2000). According to these kinds of interpretations, volitional determinism holds true for the most part, but that certain desires can (somehow) be dismissed by an act of suspension. Commentators who defend this position tend to point to Locke's correspondence with Philippus van Limborch (1701-1702) as further evidence that Locke indeed holds the mind to possess this power. If not, then there is a way to dissolve the prima facie conflict between the ability to suspend a desire and the position according to which all volitions are determined by perceptions joined to pleasures or pains. Commentators argue that it is possible to illustrate that Locke's view can be taken to be, in some, but perhaps not all ways, consistent (see Glauser: 2009; Magri: 2000; Davidson: 2013).
    In this paper, I argue that by paying close attention to the way that Locke defines 'uneasiness' - the motor for all physical and psychological change - and in particular to the way he ties uneasiness to both physical and intellectual habit-forming a way to resolve both these points of disagreement emerges. In short, I suggest, first, that the details of Locke's discussion of uneasiness indicate that he believes there to be a 'right' and a 'wrong' way to orient our uneasiness (in particular on his comments on education) thus weakening the idea that all perceived good is the real good on his system. This opens up a line of argument according to which freedom is tied to the pursuit of a particular kind of 'real' good. Second, given the nature of uneasiness and its role as the motor of change, I argue against the possibility any kind of indeterminist view of freedom in Locke's system and suggest a way to understand the power of suspension in light of the role of uneasiness. I conclude with a discussion of Locke's very infrequent appeals to the animal spirits and suggest that they are invoked as an explanatory basis for the differences among minds with respect to wants of fancy and wants of nature.