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Daniel Garber and Béatrice Longuenesse
KANT'S WORK is replete with references to his predecessors, in ancient as well as in modern philosophy. Whether positive or negative, these references are always part of Kant’s effort to set up a picture of the history of metaphysics understood as a “history of pure reason” in which each philosophical figure of the past is called upon to play its role and occupy its proper place in the gradual—albeit conflict-ridden—discovery by reason of its own power and limits, as brought to light by Kant’s critical philosophy.
Indeed, the final chapter of the Critique of Pure Reason, chapter 4 of the Transcendental Doctrine of Method, is called “The History of Pure Reason.” This title, says Kant, “stands here only to designate a place that is left open in the system and must be filled in the future” (A852/B880).1 Kant never filled that place by actually writing a “history of pure reason.” Nevertheless, the nature and goals of such a history are clearly sketched out in the few programmatic paragraphs to which the chapter in question is reduced. This sketch helps us understand what Kant means by a “history of pure reason” and thus what he is looking for in the authors he cites in the course of his own work.
A “history of pure reason,” says Kant, is a history that would be written “from a transcendental point of view” (A853/B880). As we know from the introduction to the Critique of Pure Reason, a transcendental investigation, for Kant, is an investigation into the possibility of synthetic a priori cognition—namely, into the possibility of a cognition that does not derive its justification from experience (and thus is a priori) but nevertheless does not rely on the mere analysis of concepts (and thus is synthetic). According to Kant, metaphysics is a prime example of such synthetic a priori cognition if it is possible at all as knowledge of actually existing objects rather than as a system of empty thoughts to which human reason is inevitably drawn. Correspondingly, in the preamble to the Prolegomena to Any Future Metaphysics, Kant declares that all metaphysics should come to a stop until a clear answer has been given to this question: How are synthetic a priori judgments possible? Philosophies of the past have all collapsed in a heap because of their incapacity to provide an answer to that question, indeed even to formulate it (AA 4 275-78). A similarly damning appreciation of the metaphysical endeavors of the past opens the outline of a “history of pure reason” in the Critique of Pure Reason: “I will content myself with casting a cursory glance, from a merely transcendental point of view, namely, that of the nature of pure reason, on the whole of its labors hitherto, which presents to my view edifices, to be sure, but only in ruins” (A852/B880).
But what exactly does it mean to consider the edifices of the past from the point of view of “the nature of pure reason”? It means, says Kant, examining the answers that past metaphysical systems respectively gave to three fundamental questions. First, what is the object of metaphysical cognition, namely, what is truly real? Is it an object given to sensibility, or an object accessible to the intellect alone? A prime example of the former position is Epicurus; a prime example of the latter is Plato. Second, what is the origin of metaphysical cognition: does it depend on experience or is it independent of it? A prime example of the former answer would be Aristotle and for the modern times, Locke. A prime example of the latter would be Plato and for the modern times, Leibniz. Third, what is the method to be adopted in answering the previously mentioned questions? Here Kant first distinguishes between natural and scientific method. He cannot heap enough scorn on the first (it is “mere misology brought to principles,” a dismissive statement probably directed at the commonsense philosophers he also denounced in the Prolegomena: see AA 4 258). Kant then distinguishes two kinds of scientific method, the dogmatic (whose prime example is Christian Wolff) and the skeptical (whose prime example is Hume). None of these methods, he claims, have been able to offer a satisfactory answer to the first two questions, those concerning the object and the origin of pure cognitions of reason. There remains only one: the critical method, which has just proved its superiority by the clear answers the Critique of Pure Reason offers to the questions of the object and the origin of metaphysical cognition.
Let us briefly recall what these answers were. The only reality metaphysical cognition can tell us anything about is that of sensible objects or appearances. These are real in the sense that their existence is independent of our representations, although their formal features depend on the a priori forms of our cognition. Things in themselves, namely, things as they are independently of our cognition, are real in the same sense: they too exist independently of our representations (cf. Bxxvi–vii). But these things are not, at least for us humans, objects of a purely intellectual cognition, indeed they are not for us objects of theoretical cognition at all. There is thus no synthetic a priori cognition except of appearances, sensible objects. The origin of such cognition is in the combined forms of pure understanding and pure sensibility. No metaphysical cognition can be obtained at all, at least from the theoretical standpoint, except by applying the principles grounded on these forms to some minimal empirical content: the empirical concept of matter expounded in the Metaphysical Principles of the Science of Nature (see AA 4 470). The objects of traditional metaphysics: the soul, the world, God, are not objects of theoretical cognition at all, but mere objects of thought, the contents of Ideas that have their origin in reason alone and have no more than a regulative role in cognition. In addition, the ideas of the soul and of God will turn out to have an important role as the objects of postulates of pure practical reason.
The standpoint of pure reason, then, or transcendental standpoint on the metaphysical ruins of the past, is a standpoint that is meant to confirm a contrario the correctness of Kant’s answers to the three fundamental questions on which hangs the future of metaphysics. Kant’s “history of pure reason” is a history of reason’s painful introduction to the knowledge of its own limitations. In other words, Kant’s approach to the metaphysical systems of the past is driven by concepts and concerns deliberately internal to his own system.
Of course, Kant is not the first philosopher for whom the demonstration of the collapse of previous systems supports the demonstration of the virtues of his own. Other notable examples include, for instance, Book 1 of Aristotle’s Metaphysics or Book 1, part 4 of Hume’s Treatise of Human Nature, “Of the Skeptical and Other Systems of Philosophy.” More directly close to Kant, Leibniz’s New Essays on Human Understanding had a direct influence on Kant’s presentation of the general structure of the history of metaphysics as defined by the opposition between those who think that “everything which is inscribed [on our souls] comes solely from the senses and experience”—Leibniz’s examples are Aristotle and Locke—and those who think that “the soul inherently contains the sources of various notions and doctrines”— Leibniz’s examples are Plato and himself (see NE, 48–49). And tracing back the concepts of metaphysics to the very nature of human cognitive powers is an idea that Hume, before Kant, had brought to a systematic development. But what is specific to Kant is the combined statement of the illusory nature of metaphysical endeavors, at least in the domain of “special metaphysics” (where the objects of investigation are the soul, the world, and God), the inevitability of the illusion, and its fruitfulness provided its theoretical and practical roles are carefully regimented. The history of metaphysics, conceived as a history of pure reason, thus becomes one more confirmation of the truth of the critical system. Kant gives unprecedented importance to the history of metaphysics by initiating a project in which investigating the history of metaphysics is part of investigating the nature of reason, and thus part of transcendental philosophy as the necessary preliminary to the “true” metaphysics. But precisely for that reason, the history thus expounded is, in a way, ahistorical since it is part of the timeless endeavor “to bring human reason to full satisfaction in that which has always, but until now vainly, occupied its lust for knowledge” (A855/B883).
Unsurprisingly, then, even though Kant never filled out the specific chapter on the “history of pure reason,” we can find elements of it dispersed throughout the system. The preface of the Critique of Pure Reason opens with a reference to the sorry state of metaphysics and to the opposite methods of dogmatism and skepticism that have been unsuccessfully used in trying either to answer metaphysical questions or to put them to rest. And each part of the Critique, as Kant gradually unfolds his own answer to the question of the origin and object of metaphysical knowledge, contains extensive references to the authors whose answer to those two questions Kant takes himself to be directly opposing: Newton, Leibniz, Wolff, Berkeley in the Transcendental Aesthetic; Aristotle in the Metaphysical Deduction of the Categories; Plato in the Introduction to the Transcendental Dialectic; Hume in the Methodology, with a retrospective view on Kant’s account of causality in the Second Analogy of Experience. Locke and Leibniz in the Amphiboly of the Concepts of Reflection. Des-cartes and Mendelssohn in the Paralogisms of Pure Reason. Newton and Leibniz, related back to the ancient opposition between Epicurians (“sensualists”) and Platonists (“intellectualists) in the Antinomy of Pure Reason. Descartes again in the Ideal of Pure Reason. This list is not complete, and more examples can be found in all of Kant’s published works.
This raises the question of what Kant had actually read of the authors he cites and discusses. In many cases, this question has no clear-cut answer. Kant’s library is not a reliable indicator, for we know that Kant sold or gave away many of his books. Kant lived above Kanter’s well-furnished bookstore, from which he could get a steady supply of new publications. Among the secondary sources that could have strongly influenced his view of the history of philosophy was Johann Jakob Brucker’s 1766–1767 Historia critica philosophiae a mundi incunabulis ad nostram usque aetetum deducta, a mammoth work that influenced generations of German scholars and which Kant explicitly cites in the Critique (see A316/B372). In addition, Kant’s account of historical figures was influenced by the works of post-Leibnizian German rationalists, which served as textbooks for his courses. For instance, even if it is possible that Kant read not only Des-cartes’ Discourse on the Method but also the Meditations and Objections and Replies, nevertheless his presentation of the Cartesian views, for instance his very imperfect characterization of the Cogito argument, is probably influenced by the cursory account available in Wolff’s Psychologia Rationalis, Wolff’s Psychologia Empirica, and Baumgarten’s Metaphysica. The only reasonably secure method to determine how much Kant actually knew and how he knew it, is thus to look at what Kant says, compare it to the primary sources that could actually have been available to him, and in case of discrepancies, look for other possible sources.
In any event, the systematic power of Kant’s thought is such that to this day, what counts as, e.g., “Descartes” or “Hume” or “Leibniz” in our history textbooks and our historical conscience might well be Descartes or Hume or Leibniz read in light of Kant’s reconstruction of their thought rather than those philosophers as they would have been read and understood before Kant. As a result, what exactly is novel about Kant’s own philosophy is itself somewhat obscured. Each essay in this volume is an attempt to set the record straight on both counts.
Kant deals with a number of aspects of Descartes’ philosophy. His most notorious discussion is contained in the Paralogisms of Pure Reason in the Critique of Pure Reason, in which he criticizes Descartes’ move from the proposition “I think” to the assertion that I exist as a thinking substance, distinct from the body. Other important discussions, by Kant, of Descartes’ philosophy, concern Descartes’ assertion that the existence of the mind is more immediately known than the existence of bodies outside us, and Descartes’ so-called ontological proof of the existence of God. Béatrice Longuenesse focuses her essay (chapter 1) on the first and second discussions just mentioned: Kant’s criticism of Descartes’ move from “I think” to “I am a substance whose sole attribute is to think,” and Kant’s refutation of Descartes’ “problematic idealism.” She analyzes the role Kant and Descartes respectively assign to the proposition “I think,” in the argument of the Transcendental Deduction of the Categories (Kant) and in the Second Meditation (Descartes). She then evaluates Kant’s criticism of Descartes’ move from “I think, I exist” to “I exist as a thinking substance, distinct from the body” and Kant’s refutation of Descartes’ “problematic idealism.” While endorsing, on the whole, Kant’s argument against Descartes’ move from “I think” to “I am a thinking substance,” she suggests, in contrast, that Kant’s refutation of Descartes’ problematic idealism is less successful. In his own essay (chapter 2), Jean-Marie Beyssade undertakes to set the record straight on Descartes’ behalf. He emphasizes the differences between Descartes’ views and those that Kant attributes to him. Descartes’ account of mind and its relation to body, he notes, is much more complex than Kant would have us believe. Descartes’ doctrines that the mind is something whose essence is thought, is distinct from the body, and is better known than the body, are not a simple consequence of the premise “I think.” Rather, they are established by a long and complex argument and the result of a process that takes place over the course of six “days” of meditation.
While Descartes’ presence in Kant’s work is narrowly focused on a few issues, the influence of Leibniz is much more pervasive, though ironically, more difficult to track and deal with. Leibniz was an éminence grise who stands behind much of German philosophy in the eighteenth century. His thought, as absorbed and transformed by figures such as Christian Wolff, made its way into every corner of the intellectual world. Because of that, separating out his influence from that of Wolff is very difficult. According to the standard story, while Kant began as a follower of the Leibniz-Wolffian philosophy, as he developed, he drifted further and further away. By the time of the Critique of Pure Reason, the story goes, he had fully repudiated the Leibniz-Wolffian philosophy. In her essay (chapter 3), Anja Jauernig offers an alternative account of Kant’s relation to Leibniz. While she does not deny that Kant departs from Leibniz’s philosophy in important ways, there is also an important sense in which Kant regarded himself as providing “the true apology for Leibniz,” as he puts it in one of his last works (Discovery, AA 8 250). While Kant may have seen himself as rejecting the Leibniz-Wolffian philosophy, Jauernig argues that there is a way in which Kant saw himself as a defender of the Leibnizian philosophy. Daniel Garber (chapter 4), though, emphasizes the extent to which the true Leibniz was hidden from Kant. While Kant may have thought that he was defending Leibniz, the view of Leibniz that he held was deeply influenced by the historical tradition in which Leibniz was read in the eighteenth century—a tradition that was shaped by the relatively few texts that were available to the eighteenth-century reader. Most of the Leibnizian texts that are currently taken as central were only made available long after Kant’s death. While the short and concise list of theses that, for Kant, define Leibniz’s philosophy are not entirely misleading, they fall far short of characterizing Leibniz’s complex thought, which evolved and changed throughout his career.
Both Locke and Kant were interested in the limits on our knowledge. In his Essay Concerning Human Understanding, Locke traces the path between experience and our ideas in order to determine the limits of what we can know about the world. His conclusion is that the sense organs we have determine the boundaries of knowledge. While we can have probable opinion about what lies behind those limits, the senses set strict boundaries. For Kant, too, the senses put boundaries on our knowledge, which is strictly limited to the phenomenal world of appearances. In his essay (chapter 5), Paul Guyer explores the relations between Locke and Kant on these questions. He emphasizes that while Locke’s program is largely empirical, Kant’s is transcendental. That is, while Locke argues from the empirical nature of our senses and the way in which we form ideas on the basis of the senses, Kant argues from the possibility of synthetic a priori knowledge: if synthetic a priori knowledge is to be possible, then knowledge must be limited to the phenomenal world. While Guyer acknowledges the limitations in Kant’s transcendental argument, he argues that it allows a greater scope for empirical knowledge than Locke does. On Guyer’s account, Kant believes that we can extend our knowledge beyond the deliverances of the senses through the discovery of causal laws. In that way he sees Kant’s philosophy as superior to Locke’s. Lisa Downing (chapter 6) considers these questions from the point of view of Locke. In the course of tracing the history of Locke’s views on the limitations that the senses place on the scope of human knowledge, from the early drafts of the Essay to the Essay itself and beyond to the Thoughts Concerning Education and the polemical exchanges with Edward Stillingfleet, she sees an evolution in Locke’s views that enables him to capture not only Boyle’s empirical science, but also Newton’s. In that context, she sees an openness toward new empirical knowledge in Locke’s thought that goes beyond what Guyer argues for Kant.
There are some obvious connections between Berkeley’s views and those of Kant. Both focus on the objects of our experience, and both claim that they constitute all that we can properly be said to know. There are also obvious differences, though. For Berkeley, there is nothing but minds and their ideas; Berkeley explicitly denies the mind-independent material things that others have supposed to exist. For Kant, on the other hand, while our knowledge is limited to the objects of possible experience, he does believe that behind them there are things in themselves that do have real existence, though they are beyond the possibility of our knowing. But still, one might wonder, how different are Berkeley and Kant on this question? Despite his insistent claims to the contrary, might Kant in fact be very close to Berkeley’s position? In her essay (chapter 7), Dina Emundts explores this question. On Kant’s view, Berkeley is to be understood as holding that the world of bodies is purely illusory, a position that he definitely did not want to hold. Though Emundts does consider it significant that Kant believes in the existence of things in themselves, she places more emphasis on Kant’s conception of truth and objectivity. She argues that Kant has resources that Berkeley did not for constituting real objects in an objective world. It is on these grounds that she wants to claim that Kant’s transcendental idealism does not reduce to Berkeley’s world of illusion. Kenneth Winkler (chapter 8) expresses some reservations with respect to Emundts’s readings of Berkeley and Kant. But the bulk of his essay is an explication and defense of Kant’s understanding of Berkeley. Modern scholars of Berkeley’s philosophy in general resist Kant’s view of Berkeley’s world as illusory. But, Winkler argues, there is real truth in Kant’s characterization. Winkler contextualizes Kant’s view of Berkeley in eighteenth-century conceptions of the history of philosophy. He sees Kant’s reading of Berkeley’s position—and Berkeley’s conception of his own position—as linked to Plato’s Battle of Gods and Giants, that is, the conflict between idealism and materialism, taken broadly, which eighteenth-century historians of philosophy took as a framework for understanding their contemporaries. Winkler argues that Kant, along with Berkeley himself, saw Berkeley’s position in terms of that dispute, and saw Berkeley as being on the side of the gods. In the context of that philosophical vision, it is not improper to see the physical world as illusory in a sense and of less ultimate significance than the world of spirit—again, a perspective that can be attributed to Berkeley himself.
Hume’s influence on Kant is well-known. As Kant famously put it, Hume is the philosopher who awoke him from his dogmatic slumbers (Prolegomena, preface, AA 4 260). In particular, Kant was drawn into philosophical speculation by Hume’s thought about cause and effect. Hume was interested in the way in which a cause is necessarily connected with its effect. Hume’s insight was to see the role that mind plays in determining the connection between the two. The connection between cause and effect is not something that we can learn directly from experience, Hume argues. Rather, like events associated with one another in experience produce an association between two kinds of events (fire and smoke, for example), so that when we see the one (fire), we expect the other (smoke). The necessary connection is, in that way, not in things themselves but in the mind that passes from the cause to the effect. This led Kant to appreciate the contribution that the mind could make to our perception of the world. In his essay (chapter 9), Wayne Waxman examines Kant’s response to Hume. He argues that, in a way, the whole project of the Critique of Pure Reason is itself a response to Hume. Waxman argues that Kant uses Hume’s basic strategy of looking to the senses to understand how the mind is furnished with its contents and what those contents are. But he shows how Kant had a source of sensible representation that Hume does not: for Kant, unlike Hume, the senses themselves are capable of a priori intuition. In that way, Waxman sees Kant’s thought as a broader and corrected version of Hume’s. Don Garrett (chapter 10), on the other hand, takes Hume’s point of view on the matter. From Kant’s point of view, there is something missing in Hume’s thought: had Hume only realized that mathematics and metaphysics are synthetic a priori, Kant holds, then he would have been led to transcendental idealism, just as Kant himself was. Garrett tries to show that Hume did not really need Kant’s help, and that his philosophy was quite adequate largely as it stood.
There is much left to do to understand the ways in which Kant contributed to our understanding (and perhaps misunderstanding) of the great philosophers who stood before him. The essays in this book represent first attempts at raising the right questions and sorting out the ways in which Kant related to early-modern philosophy.
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