A Companion to Kant's Critique of Pure Reason

Matthew C. Altman

• Publisher: Routledge
• Year: 2018
• eBook ISBN: 9780429982361
• Topic: Philosophie
• Subtopic: Geschichte & Theorie der Philosophie

Immanuel Kant's groundbreaking Critique of Pure Reason inaugurated a new way of understanding the world that continues to impact philosophy to the present day. With clear explanations and numerous examples, A Companion to Kant's Critique of Pure Reason takes students step by step through the book in a way that captures their interest without sacrificing depth or intellectual rigor. Although it is informed by recent Anglo-American scholarship, the Companion focuses on Kant's own arguments rather than secondary texts and scholarly debates that may otherwise distract from what Kant himself is attempting. The Companion first places the Critique in its historical and philosophical context before addressing the three main parts of the book in order: the Transcendental Aesthetic, the Transcendental Analytic, and the Transcendental Dialectic. The Companion also briefly explains how Kant continues his investigation into God, freedom, and immortality in the Critique of Practical Reason, and it concludes with an assessment of Kant's importance in the history of modern philosophy. Key features include a glossary of technical terms, with succinct definitions and cross-references, as well as an annotated bibliography of the most important English-language secondary sources on Kant's theoretical philosophy.

CHAPTER ONE

Kant’s Philosophical Environment

THE HISTORY of early modern philosophy consists of a diversity of opinions, but it can be characterized initially by philosophers’ selfconscious break with the Aristotelianism that dominated the Middle Ages. Although Aristotelianism had reigned for hundreds of years, philosophy had failed to achieve unanimity on any of the most important philosophical questions. Wild, dogmatic claims were advanced, each with its own complex and seemingly strong argument. But many of these claims contradicted one another. Metaphysical speculation about such things as how many angels can dance on the head of a pin led to unresolvable conflicts among inconsistent beliefs. What unites the early modern philosophers is a general feeling of disillusionment about the state of philosophy at the time. They attempted to right the ship by establishing a new method in order to pursue these questions more reliably. In this atmosphere of frustration and a desire for new beginnings, philosophy came to be dominated by two very different approaches, rationalism and empiricism. Both of these movements were part of what is called the Enlightenment, a period in intellectual history marked by the appeal to reason as a corrective to tradition and superstition.

Continental Rationalism: Thinking as the Way to the World

René Descartes is called the father of modern philosophy because he dramatically shifted the concern of philosophy from what is the case (ontology or metaphysics) to a consideration of how we know things (epistemology). Of course, Descartes and the other modern philosophers are ultimately concerned with the world and our place in it, just as medieval philosophers had been. But Descartes is one of the first to address what exists through an initial consideration of our own epistemic capacities. One of his most important works is the Discourse on the Method of rightly conducting one’s reason and seeking the truth in the sciences (1637). In order to discover the truth, Descartes says, we must begin by finding out how we as finite beings ought to justify our claims.

Among people unfamiliar with it, philosophy seems to involve a lot of unfounded speculation about things that we can never know. But argument and evidence—in philosophy, this usually means giving reasons—are central to the discipline, and Descartes recognizes this. To see why it is important, contrast the following two scenarios. First, imagine that you wake up in a windowless room and flip a coin: “Heads, it’s raining; tails, it’s not raining.” It comes up heads and you conclude that it must be raining. If it is in fact raining, your conclusion is correct. But now imagine that, instead of flipping a coin, you wake up, look out the window, and witness a deluge. The voice of the local meteorologist comes out of your clock radio: “We’ve already received an inch of rain today, and at this rate, we expect a lot more.” Your roommate returns with a wet umbrella and tracks mud all over the room. She says, “It’s really pouring outside.” Trusting your eyes and your ears, you conclude that it is raining, and you put on your raincoat before heading out the door. In both of these cases, you have the same true belief: It is raining. However, in which case are you more likely to say that you know it is raining? Even though the beliefs are the same and the facts are the same, you have much better evidence in the second case. True belief is not the same thing as knowledge. To know something, what you believe must also be justified in the right way.

What distinguishes Descartes and the other rationalists—most notably Baruch Spinoza and Gottfried Wilhelm Leibniz—is the claim that even this kind of (sensory) evidence is not enough. Our senses sometimes deceive us. Descartes notes that we could be hallucinating or dreaming, and it is even possible that we are constantly being deceived by some malevolent being, what he calls a “malicious demon” or an “evil genius” (M 15). The senses are undoubtedly fallible, and thus we cannot know anything with certainty on the basis of the senses alone. If sensory evidence is to be trusted—and this is a big “if”—then it must first be validated by reason. Only by reasoning can we justify our beliefs about the world and achieve knowledge of the way things must be.

Descartes begins with this surprising revelation: Everything he has come to believe has been given to him either directly from the senses (things he has experienced himself) or through the senses (things he has been taught by others or has learned as a matter of custom) (M 12). If the senses can be doubted, and if our aim is to achieve certainty, we must begin anew. The firm foundation on which Descartes tries to erect a philosophical system with scientific certainty is, famously, his own existence as a thinking thing:

But immediately I noticed that while I was trying thus to think everything false, it was necessary that I, who was thinking this, was something. And observing that this truth ‘I am thinking, therefore I exist’ was so firm and sure that all the most extravagant suppositions of the sceptics were incapable of shaking it, I decided that I could accept it without scruple as the first principle of the philosophy I was seeking. (DM 127)

Despite the ‘therefore,’ we should not be misled into thinking that Descartes is advancing some kind of typical argument, with premises and a conclusion. Rather, there is an intuitive inference from my thinking to my existing; my existence is “self-evident by a simple intuition of the mind” (M 100). If I doubt what I know, then even if I know nothing else, I at least know that I (who am doubting) exist. Of course, I do not know anything about what I am, but I know that I am.

Think of what Descartes is doing as an attempt to traverse a swamp. What had seemed like solid ground—what he thought he knew on the basis of the senses—is now a quagmire of doubt, and he is slowly testing whether there is some way to proceed. At this point, he has discovered one thing that cannot be doubted, one firm patch of ground: Cogito, ergo sum. Of course, as I think along with him, he has not proven his existence (to me). I know only that I exist. But the mere fact that I exist tells me nothing about the external world, or even if there is such a thing. At this point, I am left with only my existence and the ideas that I have in my head—if in fact I have a head. For example, I have the idea of a table. I can picture it: brown and rectangular, with four legs. On the basis of this idea, I usually make a judgment that there is an actual table out there, distinct from me, that corresponds to this idea. Although I cannot be mistaken in saying that I have the idea of a table, my claim that there actually is a table in front of me may be false. The question for Descartes then becomes: Do I have any ideas that necessarily, without a doubt, imply the existence of something besides me? This would expand my knowledge beyond the mere fact of my own existence.

I have all sorts of ideas: ideas of colors, tables, unicorns, people, historical events. Descartes thinks that all of these things could have come from me. But there is one idea that outstrips my power of imagination. The idea of God must be innate, produced in me at my creation by God himself:

By thee word ‘God’ I understand a substance that is infinite, <eternal, immutable&gt; independent, supremely intelligent, supremely powerful, and which created both myself and everything else (if anything else there be) that exists. All these attributes are such that, the more carefully I concentrate on them, the less possible it seems that they could have originated from me alone. So from what has been said it must be concluded that God necessarily exists. (M 31)

From my own existence as a thinking thing, I could have derived any of the ideas I have except the idea of God. The idea of an actual perfection could not have been produced by a limited being such as myself; it could only have come from a perfect being. Therefore, God exists.

Because the idea of an infinite perfection must have come from a being who is without flaw, God cannot be a “malicious demon.” Consequently, I know that an external world exists; a perfect being would not allow me to be constantly deceived about such a thing. Furthermore, because God is not a deceiver, I cannot err as long as I correctly use the powers that God gave me. I can make justifiable claims about the world based on the proper use of the senses. Thus Descartes validates the senses by an appeal to reason—that is, by deducing God’s existence and what logically follows from it.

From this starting point, Descartes proceeds to establish a variety of metaphysical theses, including the immateriality of the soul. I clearly and distinctly perceive myself as a thinking thing, a thing whose essence is thinking, which is not extended in space. But I also perceive my body as something different, as extended stuff for which thinking is not essential. Because God is not a deceiver and therefore would not allow what I clearly and distinctly perceive to be false, the soul must really exist as a simple (without parts), immaterial substance distinct from the divisible, corporeal body.

From my thinking alone, I have deduced that I have an immaterial soul, but what is the material world like? The nature of objects and their relations are also discoverable through reason. Sensations are caused by bodies in space but are not adequate signs of the nature of things. The senses give us fleeting perceptions that shift with a person’s perspective, vary among different observers, and change over time—color, smell, and taste are indistinct—but the fact that objects are substances is true independently of how they are perceived. Anything that is given to me in sensation is nothing but a confused form of what I already know (or can know) about the world through my thinking. We get at truth through the a priori investigation of what must be the case given the ways that we rationally conceive of the world. Thus the essence of material bodies is extension, taking up a certain space, and such pure shapes are governed by the laws of geometry. The universe consists of objects mechanically related by these immutable laws. This is the foundation of Cartesian physics.

Following Descartes’s rational method, Spinoza and Leibniz attempt to correct the fallible senses by modeling philosophy on mathematics. Like mathematics, philosophy should be an a priori investigation—that is, it should not be based on experience—that proves its claims to be necessarily true. A geometrician knows the sum of the interior angles of any triangle by determining what it must be based on our conception of a triangle, not based on the actual measurements of particular triangles. More generally, the essence of things follows logically from our rational conception of them; they are not derived from given appearances. Just as it is certain at all times and in all places that the interior angles of a triangle total 180 degrees, so too it is absolutely necessary that God exists and the soul is an immaterial thing (Descartes), that God is the one substance of which all other things are attributes (Spinoza), or that each individual substance expresses the whole universe (Leibniz).

Spinoza and Leibniz go beyond Descartes, however, in adapting mathematical reasoning more methodically to a treatment of philosophical and metaphysical subject matter. They set out to establish their claims by putting forward an initial set of definitions and axioms, which they take to be indisputable, and deriving from them all other truths (in the form of propositions). Spinoza’s “geometrical method” is modeled explicitly on the Elements of Euclid. Thus, in the Ethics (1677), Spinoza cites at each new proposition the definitions and/or axioms from which the proposition logically follows. Leibniz spells out his methodology in his essay “Primary Truths” (1689): “all remaining truths are reduced to primary truths with the help of definitions, that is, through the resolution of notions; in this consists a priori proof, proof independent of experience” (PE 31). Because all truths are generated by an appeal to axioms and definitions, neither of which depend on experience for their truth value, all truths are a priori and analytic—contained in the very concept of the thing about which the claim is being made. Reasoning can tell us what is necessarily true of the world, or even what is the case beyond all possible experience, which is more than the senses ever could tell us.

Spinoza and Leibniz draw a number of specific conclusions from this method, and they disagree on a number of points, but most of them are not important for understanding the philosophy of Kant. What is important is what makes their philosophies characteristic of rationalism: Things as they are apart from our perceptions can be known only through reason. By thinking about the nature of our ideas, God, or objects, we can determine the way things must be, regardless of what our fallible senses tell us.

British Empiricism: Furnishing the Empty Cabinet

Like the rationalists, the empiricists were similarly discouraged by the fact that there was no established method for adjudicating among the great number of competing philosophies and claims that confronted them. John Locke, the first of the British empiricists, noted that this had led to a general sense of frustration concerning the very possibility of knowledge. Thus he also devised a method that would help to distinguish sense and nonsense and that would once and for all establish certainty in the sciences. While Descartes, Spinoza, and Leibniz attempted to erect a system of ideas on the basis of rationally necessary first principles, Locke attempted a similar foundationalism, but one based on what is immediately known through the senses.

In order to establish the tenability of empiricism as a whole, Locke begins the Essay Concerning Human Understanding (1690) with several arguments against the existence of innate ideas. Only if innate ideas are first ruled out can he claim that all human knowledge is discovered a posteriori—that is, from experience, on the basis of the senses. Although Locke formulates a number of complex arguments and subarguments, his overall strategy is simple enough: Innate ideas would have to be universally acknowledged or agreed upon by all people, yet no ideas (including the idea of God) are assented to by everyone. Even when there is general agreement among the subclass of people who have “come to the use of reason” (a vague and ambiguous phrase), the fact that they do not recognize the ideas before being introduced to them is more amenable to an empiricist explanation (E 51). They agree with these claims because they have similar experiences and a shared language based on those experiences. Any disagreement with empiricism concerning the origin of these ideas is merely apparent.

If the rationalist claims that an idea is innate because people assent to it when they hear it, then that implies that everything people believe is innate. Indeed, all truths are innate in this sense, even if people never hear about them, just because they would assent to them if asked. But this way of speaking is imprecise. Instead, the capacity to know is innate; what we know is acquired. Locke himself uses the following example: Everyone would agree that “white is not black,” but how do we come to know what white and black are, and how do we learn to compare them (E 57)? We learn of these colors through the senses, and we learn to compare them by reflecting on their differences. The fact that there is universal assent to this proposition shows that those who have seen black and white can recognize that they are different. But this does not imply that the ideas were somehow implanted in us before we opened our eyes.

Of course, this is just a sketch of how Locke proceeds. But if he does in fact demonstrate that there are no innate ideas, then we must acquire them by means of the senses. Indeed, according to Locke, all ideas, even the most abstract, must ultimately be derived from perceptions:

The Senses at first let in particular Ideas, and furnish the yet empty Cabinet: And the Mind by degrees growing familiar with some of them, they are lodged in the Memory, and Names got to them. Afterwards the Mind proceeding farther, abstracts them, and by Degrees learns the use of general Names. In this manner the Mind comes to be furnish’d with Ideas and Language, the Materials about which to exercise its discursive Faculty .... (E 55)

The mind is nothing but an “empty Cabinet”—Locke also calls it a tabula rasa, a blank slate—that must be filled up with information in order for us to know anything. It gets this information from sensations that are given to it from without and from reflection on its own ideas (E 105). This is the heart of empiricism. Although we may reflect on what we are given in experience—we can compare two experiences in our head to think about how they are alike—the building blocks of what we think are provided by the world as it affects our senses. I know a table is there because I see it, or because I feel my way around it in the dark. Even abstract concepts are merely extrapolations from particular perceptions, so that when we understand classes of things or we make general claims, we do so on the basis of what we have experienced. My idea of what tables are in general is derived from common features I have noticed among tables that I have seen.

In order to clarify what we know, then, we have to examine how we sense the world and what we can claim on the basis of our sensations. To do this, Locke makes a fundamental distinction between what he calls “original or primary Qualities”—characteristics of the object itself that do not depend on how it is perceived, such as its size, shape, motion, and texture—and sensible or “secondary Qualities”—characteristics that result from how our senses are affected by the object, such as its color and taste (E 135). The difference between primary and secondary qualities can be illustrated by looking at two examples in which people make contradictory claims about what they experience. Imagine that you and your roommate go outside, and she puts on her coat because she feels cold. But you feel fine, so you say, “It’s not cold out.” In this case, neither of you is right or wrong, because what she means to say is that the tem...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication Page
• Contents
• Preface
• Acknowledgments
• Note on Sources and Key to Abbreviations
• Introduction
• Chapter 1. Kant’s Philosophical Environment
• Chapter 2. The Copernican Revolution in Philosophy
• Chapter 3. The Transcendental Aesthetic
• Chapter 4. The Transcendental Analytic
• Chapter 5. The Transcendental Dialectic
• Conclusion. Kant’s Legacy
• Notes
• Glossary of Technical Terms
• Annotated Bibliography
• Index