Critique of Pure Reason

Lecture Notes: Introduction to Kant

G. J. Mattey

Immanuel Kant (1724-1804) is considered to be among the most important philosophers in the history of Western philosophy. He made significant and influential contributions to a number of areas of philosophy, including metaphysics, ethics, aesthetics, political philosophy, philosophy of science, and philosophy of religion. Some philosophers today, especially in ethics, consider themselves to be Kantians. Kant’s accomplishments extended beyond philosophy into such areas as cosmology, psychology, and geography.

In this course we will study Kant’s most famous work, the Critique of Pure Reason, published in 1781 (and in a significantly altered second edition in 1787). We will use as a supplementary text the much-shorter Prolegomena to any Future Metaphysics (1783), which is an overview of the main themes of the first Critique. (We shall from now on refer to the Critque of Pure Reason as “the” Critique, though Kant subsequently published a Critique of Practical Reason (1788) and a Critique of Judgment (1790).)

The Problem of Presentation

Before he became a university professor, Kant published a number of short works on topics in metaphysics. He received his professorship in 1770, at the age of 46. As was the custom at the time, he submitted an inaugural dissertation, which he entitled “Concerning the Form and Principles of the Sensible and Intelligible World.” This work set the tone for his future research in metaphysics. In a letter to Marcus Herz of February 21, 1772, Kant had revealed “the plan for a work that might have such a title as The Bounds of Sensibility and Reason.” Already in his investigations, Kant thought he had found “the key to the whole secret of metaphysics that had until then remained hidden to itself.” He said that he would publish the first part of “a critique of pure reason” in “approximately three months.” It ended up taking him almost ten more years to reveal the whole of that secret—a period in which he published nothing.

As it was presented to Herz, the key to metaphysics is the discovery of way in which objects are presented to the mind. (In the Ellington translation, the German word ‘Vorstellung’ is translated as ‘representation.’ Here we follow Pluhar’s translation of the word as ‘presentation.’) The fundamental question whose answer was to provide the key to metaphysics was this: “on what grounds rests the reference of what in us is called presentation to the object?”

Kant thought that there are two easy cases in which the ground of the reference of presentation can be understood. The first case is that in which the object causes the existence of the presentation. This is what occurs with the presentations of sense. A “sensuous presentation” is a “determination of our mind” which is the effect of an object. Suppose, for example, that I see a tree. The “content” of the presentation of the tree is the way in which the tree affects me, and the presentation refers to the object (or presents it) because I have been affected by the tree. “The passive or sensuous presentations thus have a graspable reference to objects.” Kant called the capacity of the mind to be affected by objects passively “receptivity.”

If something really does affect the human mind so as to produce a presentation, there is a clear sense in which it is the “object” of that presentation and a clear sense in which the presentation has “reference” to the object it presents. But Kant makes a much more sweeping claim than this. He raises the generality of his question, inquiring into how the presentation of an object is possible at all. In his view, for an object to be the cause of a presentation, receptivity of the mind must be governed by general principles that apply to all objects of presentation. Kant claims that “the principles that are derived from the nature of our soul have a graspable validity for all things insofar as they might be objects of the senses.” This is really the central claim of Kant’s theory of presentation, and will be discussed at length in what follows.

The second easy case of reference is one in which the presentation is at least partially responsible for the very existence of the presented object. Objects are not presented to human beings in this way. For us, the presentation of the existence of an object depends on that object’s existence. But we can conceive of a being, God, whose “presentations” are models or “archetypes” for objects which that being creates. If the very existence of an object depends on a pre-presentation (so to speak) of it, then the reference of the presentation to the object is explained by the dependence of the existence of the object on the presentation. Kant called an intellect of this kind “archetypal,” as opposed to the “ectypal” (or “copying”) human intellect which receives its presentations from objects. It is obvious why any principles derived from the nature of God’s mind would apply to objects created by God on the basis of them.

So far, we have been speaking about presentations in a generic way, as if there were only one kind of presentation. But on Kant’s view, there is in fact more than one kind of presentation. The most basic division of presentations is between those in which objects are presented singularly and those in which they are presented generally.

The most obvious case of a singular presentation is one in which an object causes the presentation to exist. One might be presented with a specific tree, say the General Sherman Tree (which is by volume the largest tree in the world). This kind of presentation is called “Anschauung” by Kant, a term translated as “intuition.” He claims that for human beings, intuition exists only as the product of the affection of the mind by an object. (Kant leaves open the possibility of another kind of intuition, an “intellectual” presentation of objects, which is beyond the capacity of human beings.)

A “concept” (“Begriff”) is presentation that refers to objects in a general way. One might, for example, have a concept of a tree, which presents many possible trees without presenting any specific tree. The only way in which the concept of a tree can refer to a specific tree is indirectly. Indirect reference to objects through concepts requires a spontaneous activity of the mind, which Kant attributed to the understanding. So the understanding is the faculty of the mind which spontaneously produces concepts. Understanding is contrasted with “sensibility,” which is the receptive faculty which is responsible for the production of intuitions. The distinction between the spontaneous production of concepts and the reception of intuitions is one of the most fundamental in all of the Critique.

Now we are ready to turn to the difficult case of presentation, the one that poses a problem for metaphysics. On Kant’s view, metaphysics makes claims about objects independently of the way in which they are presented to us. The human understanding spontaneously generates concepts from itself. These concepts are “pure,” as opposed to the empirical concepts that are derived by a process of “abstraction” from the causal presentation of objects to the mind.

Kant’s fundamental question is how pure concepts can secure reference to objects. They cannot do so on the basis of their being abstracted from presentations caused by the objects. If they are derived from a causal relation to objects, then they are not “pure” products of the human understanding. Moreover, the existence of the objects to which they might refer does not depend on the understanding, as we do not have the power to create objects on our own. So why do these self-generated concepts have reference to any object at all? This, according to Kant, is the fundamental question of metaphysics.

In the Inaugural Dissertation (§8), Kant had claimed that pure concepts are to be found “in the very nature of the pure understanding.” Among these pure concepts are “possibility, existence, necessity, substance, cause, etc., together with their opposites or correlates” (e.g., impossibility as the opposite of possibility, effect as the correlate of cause). These concepts cannot be abstracted from sensory presentations because they “never enter into any sensory presentations as parts.” (Hume earlier had made the point that there is no “impression” of substance or cause. See, for example, A Treatise of Human Nature, Book I, Part 3, Section 14, “Of the Idea of a Necessary Connection.”) Nor are these pure concepts innate; instead, they are “abstracted from the laws inherent in the mind (by attending to its actions on the occasion of experience).” This claim about the applicability of pure concepts to objects lies at the heart of Kant’s metaphysical system.

In the letter to Herz two years later, Kant again claimed that pure concepts are not abstracted from sensuous presentations and hence are not produced by the objects which cause them. Nor are these concepts responsible for bringing about the existence of the objects to which they are applied.

But neither is our understanding by means of its presentations the cause of the object . . . nor is the object the cause of the presentations of the understanding in the real sense. . . . The pure concepts of the understanding must, therefore, not be abstracted from the sensation of the senses, nor must those concepts express the receptivity of presentations through sense; but they must, to be sure, have their sources in the nature of the soul, though not insofar as they are produced by the object nor insofar as they bring forth the object itself.
The problem of presentation for pure concepts of understanding is to show how these spontaneous products of the human mind have objective reference, i.e., reference to objects which they neither produce nor are produced by. A parallel problem is why pure principles of the understanding, which apply these pure concepts to objects, have “validity” with respect to these objects: “how the understanding is to lay out real principles regarding the possibility of things, and experience must faithfully agree with these principles even though they are nonetheless independent of experience.” According to the Inaugural Dissertation §8, metaphysics is “the philosophy which contains the first principles of the use of the pure understanding.” So the problem of presentation for pure concepts of the understanding is the fundamental problem of metaphysics.

The History of Metaphysics

Kant always began his university lectures on metaphysics with an account of the history of metaphysics. A version of this can be found at the end of the Critique, in a chapter entitled “The History of Pure Reason.” A brief account of the history of metaphysics can also be found in the letter to Herz. Kant was concerned not so much with the actual metaphysical principles that had been advocated, but with the way in which the philosophers tried to explain the applicability of pure concepts of the understanding to objects.

One approach is to claim that the human mind has access to the contents of the divine mind. This would solve the problem of the reference of the concepts of the understanding. We have seen that there is no problem of reference for the archetypes of objects, which are spontaneous or “intellectual” intuitions in the mind of God. If we could share in God’s intuitions, then we would be able to perform a kind of abstraction from them and derive the pure concepts of the understanding. They would not in any way be based on sensuous presentations.

Kant interpreted Plato as having come to this solution. “Plato assumed a prior spiritual intuition of Divinity as the source of the pure concepts and principles of the understanding.” (This interpretation is more reminiscent of the neo-Platonist Augustine than of Plato himself.) Nicolas Malebranche in the seventeenth century had explicitly claimed that humans have continuous access to the contents of the divine mind. Kant called this kind of system one of “hyperphysical influx.” That is, the human mind is influenced by something more than physical objects—something completely beyond the realm of physical things.

Another sort of system was advocated by Kant’s contemporary Crusius, and it can be found in one form or another in rationalists such as Descartes and Leibniz. On the system of “preestablished intellectual harmony,” the pure concepts of the understanding have reference to objects because they were placed in the human mind by God for just this purpose. In his metaphysics lectures, Kant sometimes called this kind of pure concepts “innate.”

Both of these types of systems, which rely on our relation to God to solve a problem for the human understanding, suffer from several common flaws. First, “the deus ex machina is the most absurd thing one can choose in determining the origin and validity of our cognitions.” It was always Kant’s conviction that the only plausible explanation for the origin of pure concepts of the understanding is that the understanding itself produces them. Everything else smacks of desperation or looks like some kind of cheap trick.

Second, there is a “vicious circle in the series of inferences from our cognition.” What Kant seems to have had in mind here is something like a version of the “Cartesian circle.” We could only postulate that God is the source of the validity of our pure concepts if we could prove that God exists. But such a proof would have to rely on the validity of use of the pure concepts themselves.

Finally, if we allow this kind of solution to the present problem, we should allow it for others as well. Such a solution “encourages, on a whim, any pious or melancholy chimera.” Kant was strongly opposed to any “mystical” tendencies in philosophy, as he had already shown in his 1766 treatise “Dreams of a Spirit-Seer Elucidated by Dreams of Metaphysics.”

There is another approach that has been taken by philosophers in the past, although it is not mentioned in the letter to Herz. One could simply deny that there are pure concepts of the understanding and hold that all concepts are abstracted from sensuous presentations. This is the position Kant in the Critique (“The History of Pure Reason”) attributed to Epicurus and Locke. One need not invoke the Deity to explain pure concepts because there is nothing in need of explanation. Kant rejected this empiricist approach because it would be the death of metaphysics—something he regarded as unacceptable. So the history of metaphysics leaves us with a dilemma: either we must accept a bad explanation for the reference to objects of pure concepts of the understanding and the validity of its principles, or we must give up the claim that there are any such concepts. Kant was trying to find a third way.

Phenomena and Noumena

In the letter to Herz, Kant treated the objects of sensuous presentations as being precisely those objects which cause them. But what are the objects of the pure concepts of the understanding? Are they the objects of sensuous presentations, or are they some non-sensuous intelligible objects? In the language of “the schools of the ancients” (Inaugural Dissertation, §3), are they phenomena or are they noumena?

Kant thought that as far as the human mind is concerned, the central problem is how pure concepts can refer to phenomena. They are not abstracted from sensuous presentations, so there is no causal link between phenomena and the pure concepts that would secure the reference. Moreover, Kant recounted to Herz that in the Inaugural Dissertation, “I had said: sensuous presentations present things as they appear, and intellectual ones present things as they are.” This is how rationalist philosophers had always viewed the matter.

Now if pure concepts are to represent things as they are, we must ask whether these things are the same as or distinct from things as they appear. This is a fundamental question, to which, I believe, Kant ultimately had no satisfactory answer. The Platonist school held that things as they are are exist separately (perhaps in the mind of God) as ideal archetypes, while things as they appear are poor copies of these originals. In that case, the objects of sensuous presentation are degraded and not worthy of reference through the pure concepts of the understanding.

Kant certainly rejected this point of view, for reasons we have already seen. We humans have no access to such noumena as Platonic forms. It may be that there are other ways of describing noumena. But for now, we will pass over to the view that things that appear are the same things as things as they are. That is, things as they are (noumena) appear to the human mind in a certain way through sensuous presentation, as phenomena.

This basically was the view of Leibniz and his follower Christian Wolff. According to them, sensuous presentation is a confused presentation of what is known clearly through the pure understanding. Unlike the Platonic position, which held that phenomena are degraded objects, the Leibniz-Wolff position is that the senses merely give us degraded presentations of respectable objects of the understanding. Kant rejected this position in the Inaugural Dissertation (§7) on the grounds that some sense-presentations (such as those of spatial relations) are quite clear, while some intellectual presentations (such as certain metaphysical concepts) are very obscure.

Kant’s own position was closer to that of Leibniz than to that of Plato. He held that pure concepts of the understanding have phenomena as their objects of reference. The insight that made him break with the Leibniz-Wolff position was that there is nothing degraded in the presentation of things as they appear. In effect, Kant elevated the status of phenomena by making them the objects of reference of the pure concepts of the understanding. To establish that and how this is so are the central problems of the Critique. To accomplish this end, Kant had to pay a heavy price. He had to abandon the special objects of the understanding, or at least to give them a greatly reduced role in metaphysics.

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