CHAPTER ONE.  THE CAUSE OF MOTION IS VIS ACTIVA NOT VIS MOTRIX: KANT'S FIRST SOLUTION TO THE MIND/BODY PROBLEM

This chapter is divided into six sections. The first discusses Kant's relation to the German post-Leibnizian philosophical tradition with respect to questions about change and action, monadism, and methodology. The second section focuses on Kant's understanding and criticism of a traditional view of force, change and action—the vis motrix view—that Kant thought was incompatible with mind/body interaction. I discuss Kant's alternative view, which I label the doctrine of transeunt inner change, at the end of section two and throughout section three. Section four is devoted to a close analysis of Kant's argument in Living Forces, Part I, section four that his conception of transeunt inner change can explain bodies' motions. Mine is, as far as I know, the first detailed analysis of this argument .

Section five focuses on several of Kant's general cosmological and metaphysical doctrines that help illuminate the solution to the mind/body problem he gave in Living Forces sections five and six. I discuss Kant's solution in the sixth and final section of this chapter. This section is both exegetical and critical; among my conclusions are that Kant's argument was weakened by his dogmatism and that it may have the unintended consequence of committing Kant to hylozoism.


1.1 Kant with—and against—the philosophical tradition

In this section, I situate Kant's discussion of mind/body interaction within the historical context of post-Leibnizian German rationalist philosophy. Like Leibniz, but in contrast to Wolff and others whom he referred to as Leibniz's successors, Kant believed that the metaphysical notion of action could be applied to more than changes in motion [21]. The traditional post-Leibnizian view was that the production or destruction of motion was the only way to cause changes from one state to another. Leibniz's successors used the notion of force—which they called vis motrix—to explain motion. Kant followed Leibniz in using a different concept of force, vis activa. For Kant, as for Leibniz, the concept of force could be used to explain motion, but was not used just to explain motion. As I show later in this chapter, this point was essential to Kant's earliest solution to the mind/body problem, for it made it possible for Kant to assert that bodies can exert a force on souls that has as its effect not a change in motion but the production of a representation [22].

This section is divided into four sub-sections. In section 1.1.1, I discuss two traditional questions that Kant posed about change and action. In section 1.1.2, I discuss how Kant's account of interaction was embedded in a traditional metaphysical view, monadism. In section 1.1.3, I discuss Kant's commitment to the methodological doctrine that a primary task of metaphysics is to provide a derivation of the principles of mechanics. Finally, in section 1.1.4, I introduce the central topic of this chapter, how Kant's understanding of force and motion broke from the post-Leibnizian tradition of Wolff and others.


1.1.1 Traditional questions about change and action

Kant's first writings examined two traditional questions: (I) Can individual finite substances act? If not, as the occasionalists held, each change is due to God's direct action. (II) If finite substances can act, can they act on each other? If not, change arises when each substance acts on itself. On this view, the body acts on itself to cause all its motions, the soul acts on itself to cause all its perceptions, and the appearance of interaction is due to God's harmonious arrangement of the world. Kant argued, against both occasionalism and pre-established harmony, that substances can act on each other—for example, he affirmed that perceptions are the effect of the body's activity on the soul and voluntary motion is the effect of the soul's action on the body.


1.1.2 A traditional doctrine: Kant's monadism

Kant's account of interaction was embedded in a monadology. Monadologies attempted to derive a comprehensive theory of the entire world—a cosmology—from the properties of and relations among the monadic simple constituents of the world. As a physical influx monadist, Kant was committed to explaining how real interaction takes place between the monads that underlie all matter. He faced two high hurdles, namely explaining the nature of monadic interaction and explaining why this interaction is the sufficient reason for change and order among bodies.


1.1.3 A traditional methodology: metaphysics and the principles of mechanics

Kant's early philosophy was traditional in a third way: he assumed that the principles of mechanics, which were used in the seventeenth and eighteenth centuries to explain a wide variety of natural phenomena, were correct. To be sure, there was no agreement at this time about what the principles of mechanics were; for example, there were major disagreements between Descartes and Leibniz about the laws of motion [23]. Kant assumed, first, that some set of principles was correct and, second, that it was the task of metaphysics to provide metaphysical derivations of those principles. Given Kant's monadism, the second point amounted to assuming that metaphysics should be able to show that monadic interaction is the sufficient reason for the applicability of mechanics to bodies.


1.1.4 An untraditional twist

Kant was influenced by philosophical tradition, but his views were deeply non-traditional because he argued that the post-Leibnizian rationalist understanding of motion, change, and action was incorrect. In his first published work, Kant held that Wolff and other unnamed followers of Leibniz were led to metaphysical error because they misunderstood the laws of mechanics and the nature of motion [24]. This argument occurred at the beginning of Thoughts on the True Estimation of Living Force (1747). It serves as the jumping-off point for my analysis of Kant's earliest solution to the mind/body problem in that work 23

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1.2 Kant's criticism of post-Leibnizian rationalist mechanics (Living Forces, part I, §§1-3) [25]

In this section, I discuss Living Forces, Part I, sections one through three. I am specifically concerned with how Kant's discussion of force, change, and action illuminate his solution to the mind/body problem in Living Forces sections five and six [26]. As I noted in the Introduction, Kant's views on mind/body interaction can only be understood in terms of his general account of interaction. In this section, I approach this topic by examining his criticism of a traditional post-Leibnizian view that I call the vis motrix view.

Kant thought that the vis motrix view, which maintained that bodies act only by changing motion, was incompatible with mind/body interaction because it could not explain how bodies could cause mental representations. As Kant concluded in section five, if the vis motrix view is correct, then a body's force "can at most result merely in displacing the soul from its position in space," and it could not have as an effect causing the soul to have a representation (§5; 1:20) [27]. He believed that if a body's force "can only give rise to motions," then it is impossible for that force to "generate representations and ideas" (§5; 1:20).

In section one, Kant introduced the notion of a body's essential force. On the vis motrix view, bodies had no essential force, because force was "regarded as something which is communicated from a body entirely from without" (§1; 1:17). Kant maintained that metaphysical arguments proved that bodies possess an essential force, and he criticized Leibniz's successors for adopting the anti-metaphysical methodology of looking "no further than the senses teach" (§1; 1:17) [28].

In sections two and three of Living Forces, Kant criticized the vis motrix view on two separate grounds. In section two, he argued that Leibniz's empirically-minded successors "would have been well advised to follow [Leibniz] in his metaphysical doctrines" (§2; 1:18). Instead, they used empirical observations to give Leibniz's metaphysical notion of force a more "definite" definition, but in doing this, Kant argued, they made the notion of force devoid of explanatory content.

In the next section, section three, Kant's reasoning is not entirely clear. He suggested that the vis motrix view is not just explanatorily empty, but also involves fundamental metaphysical incoherence. Kant believed that there was something incoherent in conceiving of force as something that a body has only when it is in motion. He also introduced here his vitally important criticism of the idea that changes in motion are the only effects of the exertion of force. As I discussed above, Kant's solution to the mind/body problem affirmed that bodies exert a force that can have as its effect both changes in motion and the production of mental representations.

It is important to note that Kant did affirm that bodies have a power to move and thus, in a sense, that they have a vis motrix. Kant's criticisms were directed against the specific vis motrix view adopted by Wolff and other post-Leibnizians. In section 1.2.1, I discuss this view in greater detail. In section 1.2.2, I discuss Kant's first criticism of it, his argument in Living Forces section two that Leibniz's successors attempt to define force more definitely by appealing to "what the senses teach" resulted in an empty, unexplanatory concept of force. In section 1.2.3, I do my best to interpret the extremely unclear argument of Living Forces section three, where Kant discusses the metaphysical incoherence of the vis motrix view. Finally, in sections 1.2.4 and 1.2.5, I summarize the line of argumentation that led from Kant's discussion of these topics to the solution to the mind/body problem he proposed in Living Forces sections five and six.

This section also addresses several interpretive difficulties, most notably the obscurity of section three and Kant's apparent slide between discussing force as something a body has when it moves and discussing it as something that causes changes of motion. Section 1.2.1 begins by discussing this second problem.


1.2.1 Kant's understanding of the vis motrix view (Living Forces, part I, §1)

I will begin my discussion of Kant's understanding of the vis motrix view by raising some of the philosophical tensions and interpretative problems that make Living Forces such a difficult text. Kant's discussion of vis motrix was hampered by his continual slide between two properties that the vis motrix view allegedly attributed to a body's force. In some passages, Kant treated vis motrix as a force that a body has only when it is in motion. In others, he treated vis motrix as a force that causes motion. He undoubtedly believed that these two properties were systematically linked, but he discussed neither this nor the general understanding of bodies and force that he took to be presupposed by the vis motrix view [29]. Kant could have connected the two properties of vis motrix by holding that only something in motion could cause a change in motion, but it is unclear whether he attributed this view to Wolff and other post-Leibnizian German rationalists. Fortunately, resolving these issues is not necessary for evaluating Kant's solution to he mind/body problem in Living Forces.

Kant began Living Forces "by defining certain metaphysical concepts bearing on force in bodies in general" (§1; 1:17). His definitions turned on a series of distinctions: between essential and non-essential force, between force that is internally directed and force that is outwardly directed, and between active and moving force. Like Leibniz, and in contrast to those post-Leibnizian philosophers who accepted the vis motrix view, Kant affirmed that "every body has a force essential to it" (§1; 1:17). Wolff and the other proponents of the vis motrix view held that force is inessential because it "is communicated to a body entirely from without" and it is something "in which the body does not participate when in a state of rest" (§1; 1:17). One can thus distinguish two claims that Kant made about a body's essential force. First, if a body has a force essentially, this cannot be because the force is communicated to it "entirely from without." To say that a body has a force essentially is to make a metaphysical claim that the source of that force is the body itself. Second, if a body has a force essentially, it always has the force, even when the body is at rest [30].

It is important to emphasize that, despite his agreement with Leibniz that every body has a force essential to it, Kant's own position was profoundly anti-Leibnizian. As I show later in this chapter, Kant maintained that every change involves the exertion of a transeunt or externally-directed force. This contradicted Leibniz's doctrine of pre-established harmony, according to which each substance acted only through self-affection or by the exercise of internally-directed forces. I discuss this point further when I discuss Kant's early physical influx view in sections 1.2.5 and 1.3 below.

What Kant admired most about Leibniz was Leibniz's commitment to a metaphysical methodology: Leibniz believed that a metaphysical examination of body and force was necessary to understand action, change, and motion. This methodology contrasted sharply with that adopted by the defenders of the vis motrix view, whom Kant considered to be overly enthusiastic about the role of experience in philosophy. Kant believed that, as Leibniz had taught, a metaphysical examination would show that every body has a force essential to it and therefore that the vis motrix view was incorrect. It must have seemed particularly ironic to him, therefore, that Leibniz's own successors adopted an anti-metaphysical stance that led them to consider force by "look[ing] no further than the senses teach"(§1; 1:17).

Drawing only on what they found in experience, the defenders of the vis motrix view asserted that "a body which is in motion has a force...[for example when it] overcomes hindrances, bends springs, and displaces masses" (§1; 1:17). They held that a body has force only when it causes changes of motion in other bodies, for example when a weight bends a spring or displaces a mass. Bodies that do not cause changes in motion, for example bodies at rest, were held to possess no force. This view sounds odd to modern ears, but the notions of kinetic energy and work were undeveloped in the first half of the eighteenth century [31]. This is why the defenders of vis motrix did not accept that a body at rest—for example a compressed spring or a ball at the top of an incline—can possess potential energy. In this, the defenders of vis motrix were in step with the mainstream of seventeenth century mechanics, according to which a body at rest acquired a force only when it was set into motion after colliding with a moving body. Even though he defended the contrary view that bodies have force essentially, Kant was forced to admit that the only available model of essential force, Aristotle's notion of an entelechy, was obscure and that nobody had yet "understood this mysterious teaching" (§1; 1:17).

Leibniz attributed to substance vis activa, an internal, active force modeled after the Aristotelian entelechy [32]. Kant praised Leibniz—"to whom human reason owes so great a debt"—for teaching that "in body there inheres a force which is essential to it, and which indeed belongs to it prior to its extension" (§1; 1:17). Leibniz held that a monad acts by exerting its vis activa on itself in a manner that causes its own inner perceptions to change. This idea was central to Leibniz's pre-established harmony, according to which this is the only way that monads can act. Since Kant's monadism embraced physical influx between monads, he would not have praised Leibniz for this. Rather, Kant was indebted both to the idea of the essential force of a body and to a presupposition of Leibniz's conception of active force, namely that not all action involves motion. I explain this last point in section 1.2.3, when I address Kant's confusing argument in Living Forces section three that the vis motrix view is metaphysically incoherent. I will first discuss a criticism that is easier to understand, namely Kant's claim in section two that the vis motrix view cannot be employed as an explanation for the cause of motion.


1.2.2 Kant's first criticism: the vis motrix view cannot explain the cause of motion (Living Forces, part I, §2)

Kant began section two by noting the irony that Leibniz's own followers re-interpreted his notion of an essential active force in a manner that made it accidental:

Their reliance on experience misled the defenders of the vis motrix view in two ways: they were misleadingly caused to believe that the effect of force is always a change of motion (Kant's first point in this passage) and that only bodies in motion possess force (Kant's second point). As I discus when I evaluate the argument of Living Forces section three in 1.2.3 below, Kant maintained that stationary bodies possess a force, for example "a sphere which through its weight presses upon the table on which it lies" (§3; 1:18) [33]. Nor is it true, Kant argued, that all action involves a change in motion. If this were so, then the sphere on the table would not exert a force or act in any way because it neither moves nor causes the table to move [34].

Although it illustrated the two points that Kant makes in Living Forces section two, the sphere example is best discussed when within the context of section three. Kant's main conclusion in section two was different from either of these metaphysical points, which I discuss in detail in section 1.2.3 below. He went on to argue that their reliance on empirical observation led the defenders of the vis motrix view to define force in a way that made them unable to explain the cause of motion.

If force is defined as "moving force," Kant argued, then the notion of force is unsuitable for one of its main philosophical tasks, serving as the cause of motion. If a body's force is vis motrix, then the definition of "force" presupposes the very thing that force is supposed to explain. Kant argued that to say that moving force is the cause of motion is as vacuous as claiming that a vis calorifica is the cause of heat:

It was precisely by eschewing Leibniz's metaphysical definition and searching for a more "definite" definition that accorded with common experience that Leibniz's followers squandered the promise of Leibnizian vis activa. Wolff and others did not correctly identify the cause of motion, an error that caused them to misunderstand the nature of motion and of the laws of dynamics and mechanics. To be sure, Kant did not think that the Wolffians had misunderstood the content of those laws; he admitted that the consequences of the error "do not indeed show themselves in mechanics and natural philosophy" (§5; 1:20), which is to say that the defenders of vis motrix could do mechanical calculations correctly. However, Kant concluded that construing force as vis motrix presupposed a false metaphysical understanding of the nature and source of the laws of natural science.

It is important to realize that Kant's comparison of vis motrix to vis califorica went only so far. Even if vis motrix cannot be invoked as the cause of motion, does this really show that Leibniz's followers misconceived the nature of motion? Kant attempted to show this by raising a second problem with the vis motrix view: its supporters' conception of mechanics was based on an untenable conceptual foundation because their notion of force was metaphysically incoherent.


1.2.3 Kant's second criticism: the vis motrix view is metaphysically incoherent (Living Forces, part I, §3)

Kant made this criticism in Living Forces section three, which is, word for word, one of the most obscure passages Kant published [36]. This section's ambitious scope far out-reached its scant length: Kant attempted, in just seven sentences, to discus three examples where the degree of a body's motion is not commensurate to the extent of its action and to provide at least two arguments that the vis motrix view is metaphysically incoherent. The examples used a tenet of the vis motrix view—that a body acts when it overcomes hindrances [37]—to show that "we do not speak correctly if we treat motion as a kind of action, and so ascribe to it a force synonymous with it" (§3, sentence one; 1:18).

Two of these examples were relatively clear. The first was a case of a body "to which an infinitely small opposition is made" (§3, sentence two; 1:18). When such a body moves, it overcomes almost no hindrance, for it faces only an "infinitely small" opposition. Since, as the vis motrix view itself affirms, the extent that a body acts is commensurate with the hindrances it overcomes, Kant concluded that such a body "hardly acts at all" (§3, sentence two; 1:18). However, Kant noted that such a body "has motion in an especial degree," for there is (almost) nothing opposing its motion. The case approaches that of inertial motion, which Kant defined later in Living Forces as motion that "has the characteristic of maintaining itself indefinitely...if no obstacle is set against it" (§15; 1:28) [38]. Since a body in inertial motion has no obstacle set against it, it overcomes no hindrances and, hence, according to the vis motrix view, it does not act. Although motion may sometimes be an effect of action, action is, contrary to the vis motrix view, not "synonymous" or commensurate with motion or with change of motion.

Kant also argued that there are cases of extreme action that involve the loss of all motion. He gave an example of this in the fourth sentence:

The case is one where a moving body faces an overwhelming hindrance: a moving body collides with a massive stationary body and is brought to a complete standstill. In this case, the body acts to a great extent because it expends its force on a great hindrance. Since the extent of action is commensurate with the degree of hindrance, the body is active "in the moment that it is brought to rest."

Kant concluded that vis motrix is not an "appropriate title" for the force of a body: a body in inertial motion does not act while a body acts greatly at the very moment it is brought to rest (§3, sentence seven; 1:18). The second example was meant to show that a body acts as it is brought to rest. The third was meant to show that a body could continue to act while it is stationary. Unfortunately, Kant's discussion of this example was obscure. In the fifth sentence, he referred to "bodies which act while they are at rest" and gave with no explanation the example of "a sphere which through its weight presses upon the table on which it lies" (§3, sentence five; 1:18). What is clear about this example is that it is a case where a body is not in motion. Kant believed that there is a question about whether or not such a body acts. If it is right to say it acts (as Kant apparently thought, although he gave no reasons for thinking this), Kant asserted that it is wrong to say that is does so in virtue of "striv[ing] to move" (§3, sentence five; 1:18). It is not clear what Kant meant by this, but apparently he thought that the vis motrix view would appeal to this idea and that the idea was absurd. Kant's reasoning remains obscure, but at least his point was clear enough: this example, like the other two, was designed to show that, although motion may be one effect of action, it cannot be the only effect, for the degree of action does not always correspond to the degree of motion [39].

The third and sixth sentences present at least two arguments that appear to have been meant to show that the vis motrix view is metaphysically incoherent. Unfortunately, Kant's exact conclusions, his arguments, and the relation of his arguments to the examples in the second, fourth, and fifth sentence are all obscure. The arguments focused on an idea that was connected to the examples, namely that there is no reason to assume that effects of force are only changes in motion. Of these two sentences, the sixth sentence is the clearest. It appears to be an explanation of why Kant believed it would not be satisfactory to say of the stationary sphere that it strives to move, although the sentence also seems to refer to the other two examples as well:

There is something incoherent or perhaps paradoxical, Kant suggested, in maintaining that "in so far as a body is active is strives to fall into the state in which it does not act". Unfortunately, exactly what Kant thought this objection amounted to remains unclear to me.

However obscure Kant's arguments, it is clear that he believed that their reliance on common experience led the defenders of vis motrix to erroneously assume that motion is the only effect of action. As Kant put it, "we should not, therefore, take our title for the force of a substance from that which is not an action" (§3, sentence seven; 1:18). In section 1.2.1 above, I discussed an additional reason why Kant rejected the assumption that a body at rest does not possess a force: this assumption is incompatible with every body having an essential force. If bodies at rest possess no force, then force would be something that is accidental to bodies, and that is "communicated form without" (§1; 1:17).

If the defenders of the vis motrix view were committed to the Leibnizian thesis that bodies possess force essentially, then this assumption would lead to an incoherence, for it entailed that bodies possess force accidentally. Unfortunately, this criticism is not particularly biting, because, as Kant himself discussed in section one, the vis motrix view was committed to understanding force as an inessential property of bodies. Kant's cryptic comments that the vis motrix view "maintains that in so far as it is active it strives to fall into the state in which it does not act" suggests that Kant may have had a deeper incoherence in mind, but unfortunately his reasoning is very obscure (§3, sentence six; 1:18).

Kant's overall strategy for arguing against the vis motrix view was clearer. He offered a relatively clear argument in section two that the defenders of the vis motrix view were led astray by common experience to develop a conception of force that was explanatorily empty. In section three, in a series of obscure comments, Kant discussed what he considered to be three counter-examples to the vis motrix view and he also suggested that this view was somehow deeply metaphysically incoherent. Although this last line of reasoning remains unclear to me, it may have been connected to the four main topics of Living Forces section three: first, that there is no reason to assume that effects of force are only changes in motion; second, that there is something incoherent in the assumption a body possesses force when and only when it is in motion; third, that objects in inertial motion do not act; and, fourth, that stationary objects can act.

Since the focus of this study is on Kant's earliest solution to the mind/body problem, I am obliged to set aside the interesting problems of interpreting section three. In the next section, I summarize the line of reasoning that led Kant from his criticism of the vis motrix view to his first solution to the mind/body problem.


1.2.4 A summary of Kant's argument

The first three sections of Living Forces contained a sustained criticism of the vis motrix view. In summary form, this was Kant's general line of argument:

The first claim is a point on which Kant agreed with Leibniz. Claims two and three describe positions held by Wolff and the other defenders of the vis motrix view. Claims four and five summarize Kant's two lines of criticism in sections two and three, that the vis motrix view is unexplanatory and that it assumes wrongly that all action is motion. Claim five raises two distinct points, namely that inertial motion is not action and that stationary objects can act. The second case is the most important for this study, for I have demonstrated that Kant's strategy was to show that a body can exert a force whose effect is something other than producing a change of motion. Unfortunately, Kant's explanation of this point was complex and defies easy summary; I discuss it in greater detail in section 1.4 below.

To connect these points with Kant's solution to the mind/body problem, it is necessary to draw an inference that Kant did not explicitly make:

As I show in section 2.3.1 below, in the 1750s Kant made similar points by defending his "principle of succession," which stated that "no change can happen to substances except in so far as they are connected with other substances; their reciprocal dependency on each other determines their reciprocal changes of state" (1:410). Unfortunately, the crucial claim seven does not directly follow from the argument of claims four and five, which concluded that a body's force cannot be identified with vis motrix. This lacuna is significant, for this claim was extremely important to Kant. Claim eight entailed that pre-established harmony does not reign over bodies: a body's motion cannot be explained by its actions on itself. This position, in turn, was extremely close to one of Kant's most important pre-critical conclusions, namely that bodies change only when they interact with each other or that each change involves the exercise of a transeunt force.

Kant did have an argument that bridged the gap between claim seven and his conclusion that a body's essential force is not vis motrix. This argument, which turned on the discussion in Living Forces §4 of the successive nature of the exertion of vis activa, was complex. Before discussing it in section 1.4 below, however, it will be useful to highlight the significance of claim eight by discussing Kant's early account of physical influx.


1.2.5 Physical influx and a new conception of change

Kant's argument might be extended to show that physical influx applies to bodies:

There are several difficulties with understanding the leap to this claim. An argument against pre-established harmony is not tantamount to an argument for physical influx: claim ten would follow from claim nine only if occasionalism had been proven false. Although Kant gave no direct answer to occasionalism in Living Forces, in Chapter Two I discuss why he believed that God acts to maintain the system of physical influx and does not intervene to cause each action [40].

Earlier I noted that, although he rejected the vis motrix view, Kant did not deny that motion can be an effect of the exertion of a body's force. He maintained that motion is not the only effect of vis activa and that it is not the most fundamental effect. Kant argued that motion is caused by the specific manner in which the primary effect of vis activa occurs in our world: as I show in section 1.4 below, it is only because our world is one where vis activa causes gradual change in substances' internal states that the exercise of vis activa causes changes in bodies' motion. Before explaining this, it will be useful to focus on one general point: Kant held that motion is an effect of a more fundamental action [41]. Namely, he concluded:

This more general understanding of action was the key to Kant's first solution to the mind/body problem [42]. I discuss the details of Kant's conception of change in section 1.4. Here I simply note that this idea lent support to another key pre-critical doctrine, a generalized version of the community thesis of claim ten:

Although Kant did not argue directly that a body's vis activa must be externally-directed (i.e., that a body cannot change its own states), he did argue that in every case where a body is caused to move, another body's externally-directed vis activa is involved [43]. This contrasted sharply with Leibnizian monadism, which maintained that vis activa is always internally-directed: Leibniz held that monads act on themselves to change their own perceptual states. I return to this difference between Kant's and Leibniz's understanding of vis activa in section 1.4.

 

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NOTES

21. Although Kant did not mention them by name, other members of the Wolffian camp included Samuel Formey, Johann Heinius, Johann Sulzer, and Samuel König. For good discussions of the various partisan disputes in which they engaged see Ronald Calinger's "The Newtonian-Wolffian Controversy (1740-1759), Journal of the History of Ideas 30 (1969), 319-330; Calinger's "The Newtonian-Wolffian Confrontation in the St. Petersburg Academy of Sciences," Cahiers d'Histoire Mondiale 11 (1968), 417-435; and Irving Polonoff, Force, Cosmos, Monads and Other Themes of Kant's Early Thought (Bonn: Bouvier Verlag Herbert Grundmann, 1973), pp. 24-29.

22. See section 1.6 below.

23.  I am grateful to Hannah Ginsborg for emphasizing this point in her commentary to an earlier version of this manuscript. Exactly which principles Kant took to be correct goes beyond the scope of this essay.

24.  This conclusion contrasts sharply with the traditional view that Kant was a dogmatic follower of Leibniz and Wolff at least until the "silent decade" of the 1770s. Despite recent work debunking this view—for example, by Alison Laywine, Susan Shell, and Eric Watkins—it is still common in the literature. See, for example, Graham Bird's "Kant and Contemporary Epistemology," Kantian Review 1 (1998), 1-16. For work against this tradition see Laywine, Kant's Early Metaphysics and the Origins of the Critical Philosophy (Atascadero, California: Ridgeview Publishing Company, 1993); Shell, The Embodiment of Reason: Kant on Spirit, Generation, and Community (Chicago: The University of Chicago Press, 1996); and Watkins, "Kant's Theory of Physical Influx," Archiv für Geschichte der Philosophie, 77 (1995), 285-324.

25.  I refer to Living Forces by Kant's section number and by the standard page number of the Akademie edition. When I cite long passages, I sometimes number the sentences using numbers inside editorial brackets.

26.  See section 1.6 below.

27.  I use my own translations of Living Forces, although in some cases I have modified Kemp Smith's translation in John Handyside, ed., Kant's Inaugural Dissertation and Early Writings on Space (Chicago: Open Court, 1929).

28.  I am grateful to Daniel Warren, who emphasized this point in discussion.

29.  I am grateful to Daniel Warren for pointing out this lacuna.

30.  Hegel was an astute student of Kant's understanding of substance and force. In the Science of Logic, he praised Kant, first, for providing an alternative to the vulgar Newtonian mechanism, which explained motion only "action from without," second, for arguing that matter is essentially active, and, third, for providing an account of this activity that avoided pre-established harmony. Kant's account was unsatisfactory in Hegel's eyes, however, because it did not attribute a power of self-determination to substance. Hegel argued this in "Remarks on the Kantian Construction of Matter from the Forces of Attraction and Repulsion" in the Being-for-Itself section of the Science of Logic. See pages 178-184 of A.V. Miller's translation, Hegel's Science of Logic (Atlantic Highlands, New Jersey: Humanities Press International, 1989).

31. Evaluating Hegel's argument, which made extensive references to the critical Metaphysical Foundations of Natural Science, falls well outside the scope of this study, but this is a task I hope to perform someday. For useful discussions see Sally Sedgwick's "Hegel's Critique of Kant on Matter and the Forces" in Hoke Robinson, ed., Proceedings of the Eighth International Kant Congress (Milwaukee, Wisconsin: Marquette University Press, 1995), Vol. I, Part III, pp. 963-972 and Gerd Buchdahl's "Hegel's Philosophy of Nature and the Structure of Science," Ratio 15 (1973), pp. 1-27.

32.  For a discussion of this see René Dugas, A History of Mechanics (Neuchâtel, Switzerland: Éditions du Griffon, 1955); Dugas, Mechanics in the Seventeenth Century (Neuchâtel, Switzerland: Éditions du Griffon, 1958); and Erwin Hiebert, Historical Roots of the Principle of the Conservation of Energy (Madison, Wisconsin: State Historical Society of Wisconsin, 1962).

33.  There is a large literature on Leibniz's notion of active force. Particularly useful are Margula R. Perl's "Physics and Metaphysics in Newton, Leibniz, and Clarke," Journal of the History of Ideas 31 (1969), 507-526; Joseph Agassi's "Leibniz's Place in the History of Physics," Journal of the History of Ideas 31 (1969), 331-344; and the series of essays on this topic by George Gale, including "The Physical Theory of Leibniz," Studia Leibnitiana 11 (1970), 114-127; "Leibniz's Dynamical Metaphysics and the Origins of the Vis Viva Controversy," Systematics 11 (1973), 184-207; and "The Concept of 'Force' and Its Role in the Genesis of Leibniz's Dynamical Viewpoint," Journal of the History of Philosophy 26 (1988), 45-67.

34.  Unfortunately, as I explain in section 1.2.3, Kant did not discuss this case in detail, an omission that left many confusions in its wake.

35.  This assumption was not limited to Wolff and other followers of Leibniz. For example, Descartes assumed that action of the soul on the body must entail a change in the motion of some part of the body. I am grateful to Hannah Ginsborg for helping me to understand Descartes' position.

36.  Kant argued in a similar vein in the Lectures on Metaphysics. In the Metaphysik Herder (1762-64), an enumeration of the properties of matter included "inertia (but not vis inertiae)" and "mobility (but not vis motrix)" (28:45). The contrary view was "the philosophy of the lazy" (28:48). All citations to the Lectures on Metaphysics are to Immanuel Kant: Lectures on Metaphysics, tr. and ed. by Karl Ameriks and Steve Naragon (Cambridge: Cambridge University Press, 1997).

37.  I am grateful for the extensive conversations I had with Daniel Warren about this section. He and I jointly developed the interpretation I give here.

38.  See my discussion of Living Forces §1 in section 1.2.1 above.

39.  Kant distinguished free from violent motion. Free motion is inertial motion, for example a body moving in empty space. Violent motion, in contrast to free motion, presupposes a continuing force; Kant's favorite example was an object being pushed by hand across a flat surface. In Living Forces, Kant spoke of, on the one hand, motion that "stops as soon as the driving force withdraws" and, on the other, of motion that "has the characteristic of maintaining itself indefinitely...if no obstacle is set against it" (§15; 1:28).

40.  As I explain in section 1.4.1 below, passages later in Living Forces provide evidence that Kant believed that the sphere and the table change each other's inner states through the exertion of vis activa.

41. See section 2.3 below.

42.  I discuss this in greater detail in section 1.4 below.

43.  I discuss this in section 1.6 below.