The Long View: Critique of Pure Reason


All modern philosophy is a footnote to Kant [or perhaps to Descartes], as all philosophy is a footnote to Plato. Kant is deservedly considered a great philosopher. Charles Murray puts him at number 3 in the list of the 100 most eminent philosophers. However, Kant is unusual among philosophers in having a major element of his philosophy refuted by later experimentation. Sure, sure, I hear you reciting examples of things Aristotle got wrong, like gravity. Nothing important in Aristotle's physics has been refuted. If anything, it is experiencing a resurgence. Kant's natural philosophy is radically at odds with quantum mechanics and general relativity alike.

However, the real thrust of Kant's philosophy was ethics, and this is were Kant retains enormous influence.

Kant's solution to the question of the origin of moral obligation was wonderfully ingenious, though historically catastrophic. In effect, his guiding question is not, "What would Jesus do?" but "What would I do if I were God?"

The modern turn in Kant's philosophy was to make the will the font of morality. Much later mischief has come of this.

Critique of Pure Reason
by Immanuel Kant
First Edition 1781; Second Edition 1787
Translation by F. Max Müller (1881)
Anchor Doubleday Paper Edition 1966
543 Pages, $1.95

"Immanuel admitted, as a speculative truth, that there were such things as dreams, and that he conceivably dreamed himself: but then he had a complex proof (which John never quite grasped) that no one could possibly remember a dream..."

C.S. Lewis
The Pilgrim's Regress
Page 132

All modern philosophy is a footnote to this book by Immanuel Kant (1724-1804), professor of the University of Königsberg and, by some accounts, the most boring man who ever lived. If we hold up the "Critique" to a light, we can see all kinds of creatures in embryo: Hegel's historicism, Marx's dialectical materialism, Nietzsche's Triumph of the Will, as well as such later hatchlings as Pragmatism, Logical Positivism, and Mathematical Intuitionism. There is even, perhaps, a hint of the feral supernatural that we see in the fiction of H.P. Lovecraft, which is a very late product of New England Transcendentalism. Kant's Transcendental Idealism is one of the great philosophies, fruitful even when it is wrong. Such systems are never simply refuted. Nonetheless, looking at the Critique from the beginning of the 21st century, it is clear that Kant was too pessimistic about the possible scope of human knowledge. It is also clear that, oddly enough, he had nothing to say about the real limits of pure reason.

The problem with writing about Kant is that the inherent difficulties of his philosophy are in no way mitigated by its appalling exposition. Maybe the old translation I used was more Germanic than necessary, but Kant has been blamed for inaugurating the tradition of philosophical bad prose. Kant was in fact capable of lucid writing; he even had a sense of humor. Nonetheless, the "Critique of Pure Reason," the most important of his books, is full of sentences like this: "But is it really necessary that, if effects are phenomena, the causality of their cause, which cause itself is phenomenal, could be nothing but empirical; or is it not possible, although for every phenomenal effect a connection with its cause, according to the laws of empirical causality, is certainly required, that empirical causality itself could nevertheless, without breaking in the least its connection with the natural causes, represent an effect of a non-empirical and intelligible causality, that is, of a caused action, original in respect to phenomena, and in so far not phenomenal: but, with respect to this faculty, intelligible, although, as a link in the chain of nature, to be regarded as entirely belonging to the world of sense?" (Page 372)

Let the reader be warned: there is a great deal in the "Critique" that I must have missed. Do not despise secondary sources for a more detailed account of what it says. In order to understand Transcendental Idealism, the best place to start is the apex. Although it is a full metaphysics, which treats of God, natural science and the meaning of history, the thrust of Kant's philosophy is essentially ethical. The object of morality, according to Kant, is not to be happy, but to deserve to be happy. We must live as if we were certain of the existence of God, of a future life, and of the freedom of our own wills. "The Critique of Pure Reason," oddly enough, is devoted to showing why those three key topics of philosophy can never be settled one way or the other on their merits.

What Kant did was meet the Scottish skeptic, David Hume, halfway. Hume had emphasized that all our knowledge of the world comes from sense experience. In Hume's estimation, everything that goes beyond that source is arbitrary. The apparently reliable connections we see between events in the physical world are nothing more than assumptions: causal laws can never be demonstrated with absolute certainty. Hume's skepticism also extends to the whole idea of objective moral obligation. That which should be done in a certain situation can never be deduced from a description of the situation. The lecture-room formula is that there is no way to get from "is" to "ought."

In point of fact, Hume's analysis is a parlor trick. It is certainly possible to define a situation in such a way that no moral issues arise. For instance, one might mention that one had thrown out the bath water without specifying that the baby had gone with it. Once we begin to talk about human beings and their purposes, however, a moral dimension is indeed inherent in any description we give. Kant did not take this tack, however. He accepted Hume's conclusion that morality was a product of the human mind. Rather, Kant sought to prove that the moral choices a rational mind can will are constrained. Similarly, though he also agreed that scientific laws are products of the mind, he set out to prove those products are not arbitrary, but reliably related to sensory experience.

The stricture that Kant lays down is that reason cannot tell us anything about reality beyond the world of the senses. "Beyond" includes both the supernatural and the essential nature of physical things. The underlying theme of the "Critique of Pure Reason" is that the borders of the world are as inaccessible as the receding horizon. The role of reason in this scheme is purely regulatory. Reason by itself and prior to all experience ("a priori" in Kant's famous term) cannot tell us what exists in the world. It is only with the aid of our perceptions ("a posteriori" in Kant's other famous term) that we can use reason to synthesize judgments about how those perceptions should be ordered.

Kant's solution to the question of the origin of moral obligation was wonderfully ingenious, though historically catastrophic. In effect, his guiding question is not, "What would Jesus do?" but "What would I do if I were God?" In Kant's later works, this principle was refined into the "categorical imperative." The classic formulation is: "So act that the moral of thy doing shall, at thy will, become universal law." One important implication of this principle is that morality ceases to be divine command. Another is that it makes the act of will constitutive of morality. The way was clear, then, for Nietzsche's Triumph of the Will, for Fascism and for existentialism.

What chiefly struck this reviewer were the implications of the "Critique" for physics. Kant hedges at times on this topic, and he clarified his philosophy of science in later works. Nonetheless, in the "Critique" Kant seems to say that we can never have experience of a limit to the world. Thus, we could never really prove that the universe had a beginning or is limited in space. We should always expect that material can be more and more finely divided, without any sharp division between something and nothing. In any experience, we will always find that every event has a cause. Time and space will always be found to be uniform and continuous. I could go on, but it is enough to note that Kant's philosophy seems to cast grave doubt on quantum mechanics, general relativity, and even the second law of thermodynamics. I am not at all sure that a real Kantian could accept the concepts of absolute zero or the speed of light as a maximum velocity.

The metaphysical bedrock of Kant's system is the distinction between the phenomenon (plural: phenomena) and the noumenon (plural: noumena). Phenomena are our perceptions. Noumena are the things in the world that occasion our perceptions. The twain never completely meet. Kant observes that all we know are the states of our own mind. Noumena affect those states in various characteristic ways. (A metaphor that Kant most emphatically did not use is that the mind is an FM carrier wave: the noumenon excites a signal, which is a phenomenon.) All a noumenon provides, however, is an "intuition." We can understand intuitions only because features of the mind itself order them.

Among the categories of the understanding is causality. Time and space are a priori intuitions. According to Kant, we do not get these notions from experience. Rather, it is only because of these innate features that we can have any experiences at all. The phenomena that we experience, however, are not the noumena that occasion them. We can always expect effect to follow cause in the phenomenal world. We can expect things to be bodies extended in space, and we can expect events to be ordered in time. However, those things in themselves, in the noumenal world, are fundamentally mysterious.

Kant's distinction between phenomenon and noumenon bears more than a little resemblance to Aristotle's distinction between act and potency. We may also note that, in both their philosophies, the distinction led to an ethics of self-cultivation. There is a difference between the two pairs, however. Kant's noumenal world, which he also called the "intelligible" world, is really a supernatural. Though Kant was much concerned with limiting traffic between that world and the world of phenomena, later philosophers have been less strict about controlling the border.

I will forbear to critique Kant's categories in detail, except for two points. Regarding space, Kant seems to assume that the only way we can understand it is extensively, as we do in vision. In fact, whenever he talks about geometry, indeed on most occasions when he mentions mathematics, he means Euclidian geometry. Nowhere in the "Critique," at least that I noticed, does he address the fact that space can be imagined quantitatively, as in analytical geometry. Regarding causality, both Kant and Hume seem to expect too much from it. Of course statements about the future behavior of things in the world are somewhat speculative. Their historical behavior need not be. The problem has, perhaps, been exaggerated.

According to Kant, these categories can be applied only to phenomena. When they are applied to "transcendental ideas," which are those ideas we must assume to be true for heuristic purposes, they produce arguments that cannot be decided. Kant rehearses what he calls "the antinomies of reason." These are the arguments for and against free will, God, the eternity of matter, and so on. He does not choose between them on their merits. He says, in effect, they are nonsense questions. Transcendental ideas, however, are not nonsense ideas. We must assume one side for practical purposes. Kant assures us that, though we can never prove these necessary choices, we can at least be confident that we will never be proven wrong.

"The Critique of Pure Reason" is perhaps most consulted for its critical analysis of the traditional proofs of the existence of God. Kant, in fact, is usually credited with having finally disposed of the ontological proof. This is not really the case. As Charles Hartshorne shows in "Anselm's Discovery," Kant never really engaged it. (I will not do so here, either.) Kant's real objection to the proofs (though not to God, with Whom he seems to have been on good terms) is that they extend reason beyond the phenomena of the world, beyond any possible experience. In Kant's scheme of things, we cannot use God as a First Cause, because for Kant cause is a function of the mind. We can never experience any cause as first.

Without critiquing Kant's critiques in detail, it is hard to avoid the observation that they have not aged well. His philosophy was supposed to advance the progress of natural knowledge, and no doubt it has. The problem is that, in the last century, the scientific account of the universe has progressed precisely to the kind of limits that Kant said must always recede. Kant is sometimes cited for the proposition that no empirical observation can settle a metaphysical question. His own philosophy, at least in some regards, seems to be an exception.

There is one respect in which Kant's criticisms are certainly correct. Even taken at face value, the proofs of the existence of God don't prove much. They do little more than draw our attention to a dimensionless point. Pascal once said that the god of the philosophers is an idol. This is too harsh. The proofs can play a useful role in theology, and even spiritual practice. However, there is probably a special place in Hell for people who take a mere idea as an object of worship.

Neuroscience has recently again made topical Kant's solution to the question of free will. Kant said that, considering ourselves objectively, as phenomena, we are obviously governed by physical necessity. The phenomena here include the "ego," which is a perception like any other. However, when we act subjectively, we are also obviously free. We are noumena, too; there is much more to us than the phenomena of the physical world. Indeed, the will, when acting according to the dictates of reason, is unique in being the one place where the noumenal world is known to have objective effects in the world of phenomena. Thus, though we can often find an explanation in the history of an evildoer that seems to explain his crimes, still we are always justified in holding him responsible to the standards of reason. The state of his brain, absent injury, has nothing to do with it.

There are surprises and intriguing asides in the "Critique of Pure Reason." For instance, Kant is skeptical of Occam's Razor. Reason by itself cannot tell us whether we should multiply or diminish the number of beings in the world. Another surprise is the remark that, though the argument from design for the existence of God cannot be used to demonstrate a Creator of the universe, it might be used to support the existence of an Architect. Was Kant a Mason? Were the later Masons Kantians? Intellectual history is full of surprises.

Not the least of the surprises, or at least ironies, of later intellectual history is that we know that Kant was working from a false premise. Kant believed that some metaphysical questions had never been decisively answered because reason was being applied to the wrong subject matter. He pointed to mathematics as an area where reason was rightly used: even the most abstruse questions could be settled, and all questions were answerable. Kant only hints here and there at possible insufficiencies in formal logic itself.

The 20th century ended the possibility of such complacency. Mathematics, as well as formal logic, can indeed produce well-formed statements whose truth is undecidable within the logical system in question. (An exception, interestingly enough, is Kant's beloved Euclidian geometry, which is simple enough to be complete.) Kant's controlled skepticism must be given much of the credit for these advances, though he might not have liked the results. Among them is the fact his antinomies no longer look scandalous. Now they look interesting.

Copyright © 2001 by John J. Reilly

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