The Real Meaning of Kant

by Theodore Plantinga

Every serious student of Kant at some point feels driven to put aside the commentaries, editions and learned apparatus and to ask: what is the real meaning of Kant's philosophy? The answer to this question, one might suppose, should arise out of a detailed analysis of the text, but few of the Kant scholars who have attempted to provide an analysis and interpretation of every section of the Critique of Pure Reason have succeeded in answering the question. Many of them leave us with the impression that Kant's greatest work is really a collection of philosophical doctrines and insights, a mélange of writings composed at different times during Kant's most formative and productive years but never properly integrated. But if this is the case, the frustrated reader asks, why does Kant occupy so central a place in the history of philosophy and in philosophical education?

The disappointed reader may finally pose the bold question whether there is a "real meaning" of Kant. The answer to this question, it seems to me, is both yes and no. If we mean by a "real meaning" a unified understanding of Kant apparent to anyone who takes the time and effort to make a careful study of the Critique of Pure Reason, then there is no real meaning. But if a real meaning is an understanding of Kant's philosophical labors based on one or a few unifying themes or doctrines posited as central, then there is a real meaning of Kant -- or more precisely, there are several. Various thinkers who have studied Kant have sought to unify what he accomplished by reference to one or a few key notions operative in the first Critique, but none of these readings of Kant has won general acceptance.

These unified conceptions of Kant are usually not the work of Kant scholars and commentators but rather of independent thinkers and philosophers who present a reading and assessment of Kant in the context of an exposition of their own philosophical views. Kant commentators rarely present a unified conception of Kant's thought as a whole; the numerous ambiguities and apparent contradictions in the text are largely responsible for their caution in this regard. But various independent thinkers -- most of whom have not studied Kant as carefully as the commentators -- are more willing to render a decision on what is "time-bound" in the Critique of Pure Reason and what represents the essence or heart of Kant's thought. But like the Biblical interpreters who separate "kernel" and "husk," their reading of the text often reveals more about their own thinking than about the thought of Kant. In other words the approbation and/or criticism involved in their presentation of Kant plays an important role in their respective arguments for their own philosophical positions.

The conceptions of Kant sketched below, therefore, are not interpretations in the strictest sense; some of them rest on too scanty an acquaintance with Kant's writings to qualify as such. Nevertheless, they are instructive as an indication of the many-sided character of Kant's philosophical work. And they are significant also as an indication that there is indeed a Kantian forest that can be glimpsed by the reader who takes care not to stare too hard at the Kantian trees.

Kant as Skeptic

Unlike some other important philosophers (e.g. Spinoza and Hume), Kant did not have to wait long for philosophical recognition -- although he had already reached the age of 57 when the first of his major writings, the Critique of Pure Reason, was published in 1781. It was quickly recognized as a philosophical work of great importance, but it was not immediately understood. Consequently, one of the first assessments of the Critique -- an assessment widespread and influential in Kant's own time -- was that the critical philosophy essentially represented a sophisticated skepticism. This understanding of Kant, which we might characterize as the agnostic-phenomenalistic interpretation, takes its point of departure in Kant's doctrine of the "phenomenal" character of human knowledge. Our knowledge, Kant had argued, is of appearances or phenomena -- and not of things as they are in themselves. Kant himself had admitted that Hume was an important influence on his thinking. Thus, many of Kant's contemporaries saw Kant as a re-statement or elaboration of Hume, and some even went so far as to speak of him as the "Prussian Hume."

In defense of this interpretation, it must be admitted that for Kant the object of our knowledge is indeed phenomenal. Kant repudiates the simple realism that is dear to the hearts of so many philosophers; he does not speak in terms of direct acquaintance with or apprehension of objects outside us, and he does not regard our perceptions as "copies" or accurate "reflections" of things. He does, of course, attempt to establish an inter-subjective validity that we can call "objectivity," but this is one of the more difficult sides of his teaching that escaped the attention of many of his first readers.

Kant was a critic not only of naive realism but also of the elaborate structures of metaphysical knowledge which were widely accepted in eighteenth-century philosophical circles. By limiting knowledge to experience -- or to "possible experience," as he liked to call it -- he ruled out the possibility of knowledge of trans-empirical entities such as God and the soul. To drive home the point even further, he presented what purported to be an internal critique of metaphysics in the Transcendental Dialectic, arguing that the premises on which metaphysics is based lead to direct contradictions. What made this matter all the more serious was the conviction (widespread in Kant's own time) that a theistic religious position is logically dependent on metaphysical knowledge -- especially on the proofs of God's existence, which Kant had criticized and repudiated in the Critique of Pure Reason. If Kant had destroyed metaphysics, had he not also destroyed religion? And if religion fell, could morality be far behind?

This understanding of Kant's work was summed up by one of his contemporaries, the philosopher Moses Mendelssohn (1729-1786), who spoke of Kant as the "all-destroyer" (Allzermalmer). That Kant had actually had such an effect on many of his contemporaries can easily be documented. One striking example is the German writer Heinrich von Kleist (1777-1811). Kleist had grown up an Enlightenment rationalist, and his encounter with Kant's moral philosophy confirmed him in his Enlightenment beliefs. But when he studied Kant's theory of knowledge, his life was shattered. "We cannot determine whether that which we call truth really is truth or only appears to be truth," he moaned. [NOTE 1] His "life-plan" (Lebensplan) had collapsed. "My only and highest goal has sunk," he wrote, "and I no longer have a goal." [NOTE 2] Like many of the intellectuals and writers of his time, he turned from the Enlightenment emphasis on rationality to a preoccupation with feeling and the non-rational side of consciousness. But he never found full satisfaction, and in 1811 he finally took his own life.

Kleist is only one of many writers and artists who were profoundly affected by Kant. The rise of the so-called Romantic movement in German literature is thus in part a consequence of Kant's work -- or of the agnostic-phenomenalistic understanding of Kant. Hume's skepticism about human knowledge led to his emphasis on "natural belief." Kant's alleged skepticism led to the cultivation of feeling and emotion.

Kant as Epistemologist

Another important conception of Kant's achievement is that of the critical philosophy as simply an epistemology. This conception originated in Kant's own time and -- like the understanding of Kant discussed in the previous section -- lives on to this day. The philosopher chiefly associated with this understanding of Kant is Karl Leonhard Reinhold (1758-1823), who first declared himself a disciple of Kant but later became a disciple of Fichte and then of Jacobi. Reinhold became acquainted with Kant's Critique of Pure Reason in 1785. Like many another reader of Kant, he believed that Kant's own exposition of the critical philosophy was unnecessarily complex and obscure. The real meaning of the Critique, Reinhold thought, could be stated in simpler terms, and this he proceeded to do in his Briefe über die Kantische Philosophie (Letters about the Kantian Philosophy), which he wrote in 1786. He elaborated on this exposition of Kant in other works published in the succeeding years.

Reinhold viewed the Critique as essentially a treatise on the structure and constitution of consciousness. It was a work of epistemology, then, and not of critical ontology. The question of the ultimate origin of consciousness and the question of the truth or validity of representations or ideas within consciousness were only of secondary interest, on Reinhold's reading of Kant. This version of Kant has a definite psychological flavor, and consequently the charge of psychologism has been raised against it. Later Kant scholars have reproached Reinhold for reading Kant in the spirit of Locke and of pre-Kantian Enlightenment philosophy, both of which Kant had intended to put behind him.

Reinhold seized on two pairs of concepts in his exposition of the Kantian view of representations and knowledge: the contrast between form and matter, and that between the appearance and the thing-in-itself. Every representation is a union of form and matter: the form is due to the subject and the matter to the object. The representation is thus distinct from both subject and object but at the same time essentially related to both. Reinhold made various further distinctions within this basic scheme, but the point of importance in his interpretation of Kant is the place which he gives to the thing-in-itself, namely, as that by which the subject is affected (affiziert), giving rise to the matter of representation. Kant himself had been careful to avoid such a formulation of the place of the thing-in-itself in the critical philosophy. At one point, however, he did come close to Reinhold's position: "How things may be in themselves, apart from the representations through which they affect us, is entirely outside our sphere of knowledge." [A190/B235, italics mine] But his standard view is that causal language cannot be applied to the relation between intuition and the thing-in-itself, for the concept of causality is valid only within the horizon of experience and thus cannot be applied to trans-empirical entities. But where does the matter of representation originate, if not in the thing-in-itself? In the Introduction to the Critique Kant leaves open the possibility that sensibility and understanding "... spring from a common, but to us unknown, root." [A15/B29]

Representation, then, is the result of the subject's imposition of a form on the sense material contributed by the thing-in-itself. Knowledge is simply our consciousness of this represented object. The appearance, the object of our knowledge, is thus a representation of the thing-in-itself, but within the form imposed by the understanding.

It cannot be denied that Reinhold's version of Kant is much easier to understand than the Critique itself -- hence its quick popularity. Reinhold's error lay not so much in a particular misreading of the text as in his focus. In Ernst Cassirer's words: "With this introduction of the problem Reinhold has really grasped only a limited section of the universal Kantian problematics ...." [NOTE 3] This partial grasp led to a serious distortion of Kant's doctrine of the thing-in-itself. Yet it was Reinhold's statement of this doctrine that critics of Kant like G.E. Schulze (in his Aenesidemus) and J.G. Fichte had in mind when they declared that the doctrine of the thing-in-itself is untenable.

Reinhold's version of Kant is still of interest to us today because many readers of Kant come up with a roughly similar account of the Critique and especially of the doctrine of the thin-in-itself in their first encounter with Kant's magnum opus. If Kant were only an epistemologist concerned to give us an account of representation and our awareness of objects, both Reinhold's interpretation and Schulze's criticism would merit close attention.

Kant as Philosopher of the Ego

Although Kant had made it clear that he regarded the Transcendental Deduction of the Categories as the heart of the Critique of Pure Reason, his doctrine of the thing-in-itself was the focus of much of the early debate about the real meaning of Kant. As we have seen, it was Reinhold's mistaken formulation of this doctrine that set the stage for this discussion. G.E. Schulze (1761-1823) quickly made it clear that the doctrine of the thing-in-itself as the cause of intuition or the given in sensation is inconsistent with the rest of Kant's teaching. The same conclusion was reached by the most important of Kant's early followers, J.G. Fichte (1762-1814), who presented his own philosophy as a fulfillment of the real meaning of Kant's work.

The overriding concern of Fichte's philosophical career was morality. The evolution of his thinking was heavily influenced by his preoccupation with the problem of freedom and determinism. When he became acquainted with Kant's philosophical work in 1790, he seized on it as the answer to this philosophical and moral dilemma. He then made Kant's acquaintance and soon won his approval by writing a treatise on revelation (entitled Kritik aller Offenbarung, i.e. Critique of All Revelation) along Kantian lines. He went on to write and publish other works, but Kant soon felt compelled to protest that what Fichte was saying was a deviation from the critical philosophy. Kant and Fichte then quarreled over the real meaning of Kant's philosophical work, and Fichte continued to regard his own work as a logical extension of that of Kant.

Fichte did not share Kant's love for balance and symmetry, and thus he could not bring himself to view the doctrine of the thing-in-itself as a necessary part of the structure of the critical philosophy. Not only was the doctrine inconsistent with the critical philosophy, Fichte believed, but it led to skepticism. In a letter to Reinhold he wrote: "As long as we retain the notion of a connection between our knowledge and a thing-in-itself which is supposed to have reality completely independently of it, the skeptic will be able to carry the day." [NOTE 4] If the thing-in-itself is not the ultimate ground of the matter of representation, then Kant's suggestion of a common root of sensibility and understanding (A15/B29) might merit close attention. This was the path that Fichte himself chose to follow.

Although Fichte's magnum opus was entitled The Science of Knowledge (Die Wissenschaftslehre), his chief philosophical concern was not with epistemological questions but with what we would probably call ontological and moral questions. It was Kant's moral philosophy, his doctrine of human freedom, that attracted him. Yet Fichte did not limit his attention to the Critique of Practical Reason; the major idea underlying his own thought was already expressed in the first Critique. Like many other readers of Kant, he was struck by the idea that "... the conditions of the possibility of experience in general are likewise conditions of the possibility of the objects of experience ..." (A158/B197). Richard Kroner, who interprets Kant from a standpoint sympathetic to post-Kantian idealism in his book Von Kant bis Hegel, has said of this sentence that it "... contains the nucleus of Kant's entire theoretical philosophy." It justified the conclusion "... that Kant actually identifies conditions of being with conditions of knowing, and that in this regard his thinking too is of a logical-ontological character." [NOTE 5] The real meaning of Kant, then, lies in his ontology or metaphysics -- and not in his epistemology. Kroner goes on to say: "The decisive step beyond all previous metaphysics which Kant takes is the step from the philosophy of the world to the philosophy of the ego." [NOTE 6] Kroner explicates this as follows: "The ego is, simply, the supreme and highest principle of the possibility of experience and of objects. Without the ego which pronounces the judgments of knowledge and for which the judgments are valid, without a consciousness in which the subject and the predicate of the judgment are connected and for which the connection has the value of truth, neither experience, i.e. knowledge of things, nor an object of experience, i.e. the being of things, is thinkable." [NOTE 7]

Fichte's own philosophical work was an extension of this philosophical tendency, which comes to definite expression in Kant. (Whether it actually governs Kant's thought is another question.) For Fichte, then, Kant is the philosopher of the ego. In one bold stroke, Kant had overcome the threat to morality and human life itself implied in the determinist view of the world. The ego is primary both morally and ontologically. Because of its ontological primacy, because it is the ultimate condition of the existence of objects, of nature, of the non-ego, nothing can stand in its moral path.

Fichte once wrote of his own philosophy: "If the system of knowledge were asked how the things-in-themselves are constituted, it could give no other answer than: in just the way that we must make them." [NOTE 8] This sentence, according to Kroner, reveals the heart of Fichte's philosophy and could well be regarded as its motto. A moral necessity residing in nothing other than the ego is the ultimate principle by which we must explain both knowledge and being. This, for Fichte, is the real meaning of Kant.

Kant as Metaphysician

While Fichte saw in Kant the founder of a new metaphysics of the ego, later nineteenth-century thinkers were more inclined to view his achievement in relation to classical philosophical conceptions far removed from the idealism of Fichte, Schelling and Hegel. To nineteenth-century positivists who raised the "back to Kant" cry, this idealism was a grandiose philosophical error, but to Arthur Schopenhauer (1788-1860) it was an abomination. Schopenhauer, who passed up no opportunity to express his contempt for Fichte and Hegel and to heap scorn upon them, saw Kant as a metaphysician in a more classic sense, i.e. a metaphysician concerned with what is behind or beyond the world of sense and appearance.

Schopenhauer was certainly a more careful student of Kant than most of the other philosophers to be discussed here. He first became acquainted with Kant's thought through the second edition of the Critique of Pure Reason; when he later read the first edition, he declared it to be superior to the second. It was Schopenhauer's considered judgment that Kant had spoiled -- and even mutilated -- his masterpiece by publishing the second edition, for on his view it included mistaken formulations which proved the basis for much of the subsequent debate about the real meaning of the critical philosophy.

Schopenhauer made his view of Kant known in his "criticism of the Kantian Philosophy," which he published as an appendix to The World as Will and Representation. This Criticism, which also includes a good deal of praise, opens with the words: "It is much easier to point out the faults and errors in the work of a great mind than to give a clear and complete exposition of its value." Equally significant is the epigraph, taken from Voltaire: "It is the privilege of true genius, and especially of the genius who opens up a new path, to make great mistakes with impunity." It is in this spirit, then, that Schopenhauer approaches Kant's work. He singles out its primary achievement and presents his own work as a fulfillment of the real meaning of Kant.

Kant's achievement was to establish idealism -- or rather its ascendancy in Europe. "Thus before Kant we were in time; now time is in us," Schopenhauer wrote. [NOTE 9] The basis of this idealism is Kant's central doctrine: "Kant's greatest merit is the distinction of the phenomenon from the thing-in-itself, based on the proof that between things and us there always stands the intellect, and that on this account they cannot be known according to what they may be in themselves." [NOTE 10] This positing of a reality behind the world of sense appearance is really what the religions -- especially the non-Mohammedan religions of Asia -- have long taught. The gap between the real and the ideal accounts for the transient and illusory character of much of our experience. According to Schopenhauer, "Such clear knowledge and calm, deliberate presentation of this dreamlike quality of the whole world is really the basis of the whole Kantian philosophy; it is its soul and its greatest merit. He achieved it by taking to pieces the whole machinery of our cognitive faculty, by means of which the phantasmagoria of the objective world is brought about, and presenting it piecemeal with marvelous insight and ability. All previous Western philosophy, appearing unspeakably clumsy when compared with the Kantian, had failed to recognize that truth, and had therefore in reality always spoken as if in a dream. Kant first suddenly awakened it from this dream; therefore the last sleepers (Mendelssohn) called him the all-pulverizer." [NOTE 11]

Schopenhauer was by no means unaware of the epistemological side of Kant's thinking; throughout much of The World as Will and Representation he tries to re-cast Kant's theory of knowledge in a more acceptable form, relating it to empirical scientific factors which Kant had unfortunately ignored. Yet the doctrine of the thing-in-itself remained Kant's central merit. Schopenhauer agreed, however, with some of the earlier criticisms of the doctrine, and he substituted his own justification of the doctrine for that presented by Kant. "It is certainly remarkable," Schopenhauer wrote, "that he did not trace that merely relative existence of the phenomenon from the simple, undeniable truth which lay so near to him, namely, `No object without a subject', in order thus, at the very root, to show that the object, because it always exists only in relation to a subject, is dependent thereon, is conditioned thereby, and is therefore mere phenomenon that does not exist in itself, does not exist unconditionally." [NOTE 12]

For Schopenhauer, the thing-in-itself is more than a mere unknown which we posit as a limit on our knowledge. We have an intuition of it in our willing acts, for it is itself will. The ultimate reality is the Will, and the entire world of appearance must be regarded as its expression -- hence the title of Schopenhauer's major philosophical work: The World as Will (noumenon) and Representation (phenomenon).

In the Critique of Pure Reason Kant claimed to have abolished metaphysics as a science of trans-empirical entities. But for Schopenhauer, metaphysics in this sense represents the real meaning of Kant. What else is the celebrated thing-in-itself if not trans-empirical?

Kant as Pragmatist

It might seem odd to think of Kant as a pragmatist, for pragmatism as a philosophy is a late nineteenth and early twentieth century phenomenon. (The word "pragmatic," of course, is much older.) But at least one representative of a pragmatist view of truth has pointed to Kant as one of the sources of the idea that utility is the test for truth. Hans Vaihinger (1852-1933) is perhaps best known to students of Kant for his important commentary on the first Critique (published in 1881-82) and for his sponsorship of the controversial "patchwork thesis" about the composition and meaning of Kant's Transcendental Deduction. His view of the deduction entitles us to conclude that he is less than a fervent admirer of Kant. Since Vaihinger did not live at a time when Kant's influence was overwhelming -- as did Reinhold and Fichte -- he was able to evaluate and assess Kant's achievement in a more detached way. On his view, what is of greatest value in Kant is the notion behind the little phrase "as if," which occurs at some key junctures in Kant's writings.

Kant had drawn a distinction between the theoretical employment of pure reason and its practical employment, but the gulf between the two is not as large as some of Kant's readers have supposed. In the preface to the second edition of the Critique of Pure Reason Kant had written: "I have therefore found it necessary to deny (aufheben) knowledge, in order to make room for faith." [Bxxx] This Aufhebung or limitation of knowledge is part of the task of the first Critique: human knowledge is phenomenal in character and does not extend to things-in-themselves. This rules out all metaphysical claims, including the doctrines of God, freedom and immortality. But these three are re-instated in Kant's moral philosophy, as postulates necessary for morality. This re-instatement is only possible because of the critical limitation or denial of knowledge. Because all knowledge is limited to experience, we can neither affirm nor deny (on purely theoretical grounds) the existence of God, the immortality of the soul, or the freedom of man as he is in himself (rather than as appearance or phenomenon). All three of these doctrines are necessary for morality; without them morality would make no sense. (It was inconceivable to Kant that morality would not ultimately be rewarded.) Kant therefore bestows on them the status of postulates and tells us that we must act as if they were true.

The realm of the "as if" is not limited to morality. Kant's theory of science also includes "as if" beliefs, which function as heuristic principles. In the Transcendental Dialectic Kant distinguishes between constitutive and regulative uses of the ideas of pure reason. The constitutive use of such ideas would result in empty notions bearing no relation to experience and therefore unworthy of the name "knowledge." But ideas of pure reason employed in a regulative manner help us to unify and systematize our knowledge of nature. "These concepts of reason," Kant writes, "are not derived from nature; on the contrary, we interrogate nature in accordance with these ideas, and consider our knowledge as defective so long as it is not adequate to them. By general admission, pure earth, pure water, pure air, etc. are not to be found. We require, however, the concepts of them (though, in so far as their complete purity is concerned, they have their origin solely in reason) in order properly to determine the share which each of these natural causes has in producing appearances." [A645-6/B673-4] Another such idea is that principles and entities must not be unnecessarily multiplied, i.e. that we must seek the simplest explanation. This principle too has its origin not in experience but in pure reason, and it also plays an important role in the quest for systematic knowledge of nature.

One of Kant's reasons for writing the Critique of Judgment was to try to bring the theoretical standpoint of the Critique of Pure Reason and the practical standpoint of the Critique of Practical Reason closer together. The notion of purpose or teleology in nature was of use to him in this regard. This notion cannot be derived from an analysis of phenomena; it too has its origin in reason. Kant claims that it is sometimes helpful to describe the phenomena with which the scientist deals in terms of purpose. (The language regularly used by biologists seems to support Kant on this score.) Consequently, the scientist should look at nature as intelligible, i.e. as possessing the kind of intelligibility it would have if it had been created by an omniscient and omnipotent God. This regulative use of the idea of purpose lays upon science the obligation never to halt in its quest for scientific explanations but always to press on, in the faith that even the most minute details in nature possess their own intrinsic intelligibility.

From the regulative use of ideas stemming from pure reason to a pragmatist justification of such ideas is but a short jump. Could Kant not be understood to mean that any idea or hypothesis which is useful in science or praxis (moral life) should be regarded as true? Hans Vaihinger, in any case, regarded the suggestion of such a notion of truth as the most valuable and fruitful side of Kant's thought. His commentary on the first Critique grew out of a prior interest in the notion of the "as if" in Kant. Vaihinger himself developed this notion in some detail, and the result was a book entitled The Philosophy of "As If": A System of the Theoretical, Practical and Religious Fictions of Mankind (first published in German in 1911).

Vaihinger tells us that what appealed to him most in Kant was his emphasis on the practical aspect. "I derived permanent value not only from his theory of the limitation of knowledge to experience," he wrote, "but also from his doctrine that action, the practical, must take the first place, in other words the so-called supremacy of practical reason." [NOTE 13] Vaihinger regarded his own philosophy as a union of idealism and positivism, but a good part of The Philosophy of "As If" is devoted to a discussion of the "as if" in Kant. Vaihinger elaborates his own version of the "as if" in terms of a doctrine of fictions, which he defines as "... hypotheses which are known to be false, but which are employed because of their utility." [NOTE 14] In declaring these fictions to be false, Vaihinger of course goes beyond Kant's own position. But the justification of principles used in science and life on the basis of utility is definitely approved by Kant, and therefore the pragmatist notion of truth or utility might conceivably be regarded as Kant's greatest achievement.

Kant as Dualist

Vaihinger's assessment of Kant's achievement focuses on the relation between theoretical reason and practical reason. Yet this relation is ignored by many of the philosophers who regard themselves as carrying on the tradition of Kant, for the theoretical philosophy of the first Critique is by itself a rich enough source of inspiration and insight. But for Kant's critics, the relation between the theoretical and practical realms might be seen as central to understanding Kant's philosophical labors -- and perhaps also central to his failure. The publication of the third of the critiques can be viewed as an indication that Kant himself was uneasy about this matter.

If Kant's practical and theoretical realms have not been brought into proper relation, then we might view Kant as a dualist without a properly unified and integrated conception of reality. This is the kind of approach to Kant taken by Herman Dooyeweerd (1894-1977), who sees the freedom-determinism problem as the heart of Kant's thought. Dooyeweerd discusses Kant at some length in A New Critique of Theoretical Thought, his three-volume magnum opus. Coming from a neo-Kantian philosophical background, Dooyeweerd regards a critical assessment of Kant as necessary in his exposition of his own system. He respects Kant deeply for his magnificent grasp and presentation of the central motive of modern Humanism, but he regards him as profoundly wrong.

On Dooyeweerd's view, the tension between determinism and freedom, the ideal of science and the ideal of free, sovereign personality, has dominated modern western culture and thought. The Christian philosophical position for which Dooyeweerd argues can be justified only in conjunction with a critique of the Humanist philosophical tradition, for Humanism and Christianity have been very closely intertwined throughout history. In other words, a Christian philosophy is possible only if it includes a critical assessment of the Humanist philosophical tradition. Dooyeweerd's confrontation with Kant is thus no peripheral part of his own philosophical project; it occurs not in an appendix but in the first volume.

The tension between the two poles of nature and freedom comes to sharpest expression in man's knowledge of himself. Man is part of nature and thus subject to its determination. Yet he affirms his own freedom over against nature and his fellow man. When the Humanist tradition makes man, i.e. human reason, the sovereign law-giver of nature, it creates a theoretical dilemma, for he is then subject to laws that have their grounds in him. Humanism affirms its belief in human worth and dignity by making man sovereign in the universe -- but it leaves this autonomous man bound by his own laws and, thereby, not autonomous. To circumvent this difficulty, a second sphere is posited in which man is also the law-giver (i.e. the moral sphere) but in which the validity of the laws is of a different character, i.e. they demand a free response.

That these considerations are central to Kant's thinking is evident from the preface to the second edition of the Critique of Pure Reason. Man's sovereignty as law-giver for nature is absolute: everything in the realm of appearance (i.e. nature) is regarded as determined in accordance with the principle of causality, which owes its origin and validity to the understanding. Therefore, the ego as an empirical manifestation is also determined. Here the ideal of science wins out. But in Kant's balanced dualism, the ideal of free, sovereign personality quickly recovers much of the ground lost: "... if our Critique is not in error in teaching that the object is to be taken in a twofold sense, namely as appearance and as thing in itself; if the deduction of the concepts of understanding is valid, and the principle of causality therefore applies only to things taken in the former sense, namely, in so far as they are objects of experience -- these same objects, taken in the other sense, not being subject to the principle -- then there is no contradiction in supposing that one and the same will is, in the appearance, that is, in its visible acts, necessarily subject to the law of nature, and so far not free, while yet, as belonging to a thing in itself, it is not subject to that law, and is therefore free." [Bxxvii-xxviii] Morality requires only that freedom "... should not contradict itself, and so should at least allow of being thought, and that as thus thought it should place no obstacle in the way of a free act (viewed in another relation) likewise conforming to the mechanism of nature. The doctrine of morality and the doctrine of nature may each, therefore, make good its position." [Bxxix]

For Dooyeweerd, this sharp separation of the practical from the theoretical, the noumenal from the phenomenal, shatters the coherence of reality. "The Critique of Pure Reason and its counterpart the Critique of Practical Reason," he writes, "break the cosmos asunder into two spheres, that of sensory appearance and that of super-sensory freedom. In the former, the ideal of science is lord and master; the mind is the law-giver of nature, since it constitutes empirical reality as `Gegenstand.' But the ideal of science with its mechanical principle of causality is in no way deemed competent in the super-sensory sphere of moral freedom. It is not permitted to apply its categories outside the domain of sensory experience. In the realm of moral freedom the 'homo noumenon' (the humanistic ideal of personality in the hypostatized rational-moral function) maintains its own sovereignty." [NOTE 15] The unresolved dualism of the nature-freedom antinomy is the reason for the course taken by post-Kantian speculation. Kant had left philosophy in an untenable position, and therefore he had no followers in the strict sense. Fichte chose boldly for one side of the polar tension by positing the absolute freedom and primacy of the ego. He therefore made nature and the science of nature subordinate to the sovereign, free personality (i.e. Spirit). In Fichte's philosophy, nature's being is a being-for-another, i.e. for Spirit.

Many philosophers later in the nineteenth century repudiated Fichte's choice in the strongest terms and opted instead for the ideal of science, denying human freedom and asserting that everything that happens accords with scientific laws and is predictable in principle. Kant's attempt to balance and harmonize the two opposed poles of nature and freedom failed, and the tension between the two continues to this very day.

For Dooyeweerd, this tension at the heart of the Humanist philosophical tradition is dialectical in character. An affirmation of one of the poles quickly calls forth a response on behalf of the other, and thereby the opposition between the two takes on ever new forms. This is the reason for the popularity of dialectical modes of thinking in the nineteenth and twentieth centuries. The tension takes on its sharpest form in thinking about man himself; man is regarded both as transcendental source and origin of all meaning and law (Kant's transcendental ego) and as a finite being conditioned in the same way as all other finite entities (Kant's empirical ego). The failure of modern science to produce a unified, total view of man is rooted in this tension between man as sovereign and autonomous and man as a conditioned part of the natural order. The real meaning of Kant, for Dooyeweerd, lies in his explicit awareness and statement of the antinomy of nature and freedom.

Kant as Phenomenologist

As we have seen, most philosophers who take a positive or approving attitude toward Kant tend to regard him as a forerunner of their own philosophical positions; the real meaning of Kant lies in whatever elements or side of his thinking that might point in their direction. Edmund Husserl (1859-1938), the father of phenomenology, is no exception. Yet, Husserl began his philosophical career with a very low estimation of the value of Kant's philosophical labors. He inherited this conception of Kant from his teacher Franz Brentano (1838-1917), who was himself a philosopher of considerable importance. Brentano regarded the history of philosophy as repeating a cycle made up of four phases. The ancient, medieval and modern periods each represent one complete cycle. The first of the four phases is ascent and bloom. It is followed by a leveling out, which is characterized by a lack of interest in scientific questions, by sterile, scholastic disputes, and by superficial popular philosophies. This is in turn followed by a skeptical stage. The fourth and final stage represents a response to this skepticism: philosophy degenerates into an arbitrary, anti-skeptical dogmatism, appealing sometimes to a special source of knowledge and even retreating into mysticism. This final dissolution of philosophy in the ancient world is represented by neo-Pythagoreanism and neo-Platonism; in the modern world it is represented by Kant and post-Kantian idealism. In Kant's philosophy the mystical element comes to expression in the appeal to "synthetic a priori" judgments. [NOTE 16]

At first Husserl accepted Brentano's assessment of Kant as a philosopher who tried to counter skepticism with dogmatic, unfounded claims and appeals to the mystical. But as the years went by and he himself began to develop in a direction reminiscent of Kant, he came to realize that he had not understood Kant properly. From Iso Kern's book Husserl und Kant, we learn that Husserl spent a good deal of time studying Kant during his later years. In the Cartesian Meditations (written about 1929-30) he developed a position that can be characterized as a transcendental idealism, a position that is fairly close to the transcendental idealism of Kant. (In the very last years of his life he moved on to yet another position further removed from Kant.) Much of Husserl's later work can therefore be viewed as an Auseinandersetzung with Kant, i.e. an attempt to define his own position in relation to that of Kant and the neo-Kantians.

Husserl's mature assessment of Kant's philosophical achievement came to expression in 1924 in an article on Kant and the idea of transcendental phenomenology, which was written for the occasion of the 200th anniversary of Kant's birth in 1724. Although he was by no means uncritical of Kant, he did credit him with discovering the central phenomenological doctrine of the intentional character of consciousness. Kant's legacy, Husserl declared, must not be given up but must be preserved eternally by clarifying and developing its content. He further declared that phenomenology is itself an attempt too be true to the deepest meaning of Kant's philosophical activity. But Husserl stopped short of calling himself a Kantian or a neo-Kantian. Writes Kern: "Despite his consciousness of an inner affinity, Husserl did not want to be understood on the basis of Kant or neo-Kantianism; on his view, it is instead the critical philosophy which can be grasped clearly and in its true merit only on the basis of transcendental phenomenology." [NOTE 17] For Husserl, then, phenomenology is a realization of the real meaning of Kant.

Kant as Ontologist

The affinity between Kant and phenomenology also comes to expression in the philosophical career of Martin Heidegger (1889-1976), who aligned himself with the phenomenological movement -- although he was never Husserl's disciple in the strict sense -- and became strongly interested in Kant at about the same time. Being and Time (1927), the major publication of Heidegger's so-called phenomenological period, was viewed by its author as a fulfillment of the real -- if sometimes unexpressed -- philosophical intentions of Kant. To someone familiar with Heidegger's magnum opus, this claim may appear very bold -- if not downright false. But Heidegger has definite ideas of his own on how philosophers of the past are to be read and understood. In his book on Kant (Kant and the Problem of Metaphysics, first published in German in 1929), he tells us that he is not interested in paraphrasing Kant but in getting at what Kant "intended to say." He adds: "It is true that in order to wrest from the actual words that which these words `intend to say,' every interpretation must necessarily resort to violence. This violence, however, should not be confused with an action that is wholly arbitrary. The interpretation must be animated and guided by the power of an illuminative idea. Only through the power of this idea can an interpretation risk that which is always audacious, namely, entrusting itself to the secret élan of a work, in order by this élan to get through to the unsaid and to attempt to find an expression for it. The directive idea itself is confirmed by its power of illumination." [NOTE 18]

The illuminative idea used to interpret a thinker must be central to both the thinker's thought and the interpreter's own thinking. Thus Heidegger, like other philosophers who have made pronouncements about the real meaning of Kant, seizes on a particular side of Kant's thinking and uses it to interpret the whole. His choice, as one might guess, is the doctrine of time. The point of Heidegger's own magnum opus is to demonstrate the temporality of being; in Kant's emphasis on the thoroughly temporal character of our experience Heidegger sees an earlier and somewhat inadequate attempt to grasp the same truth. But Kant's position in a tradition prevented him from breaking free in such a way as to be able to grasp the full significance of temporality; the importance of the future dimension, for example, largely escaped his attention. For this reason Kant has often been misunderstood: commentators have viewed him as presenting a theory of experience or a theory of science. What Kant was really presenting, according to Heidegger, is a doctrine of being, an ontology.

Being is Heidegger's central concern in Being and Time, but he approaches this question through an explication of the kind of being closest to the inquirer, i.e. the being of man himself. Kant should likewise be read as presenting us with a theory of man, for the basic questions of ontology and of philosophy itself come to sharp focus in the question of man. No previous epoch, Heidegger points out, has possessed as much knowledge of man as our own, yet in no other epoch has man appeared as mysterious as in ours. He quotes with approval Max Scheler's claim that "In a certain sense, all the central problems of philosophy can be reduced to the question of man and his position and metaphysical situation within the totality of Being, the world, and God." [NOTE 19]

What is it that Kant had revealed about man? In insisting on the doctrine of the thing-in-itself, he had pointed to human finitude -- a lesson quickly forgotten by his idealist successors. He formulated this insight in terms of an emphasis on the finitude of human knowledge. The doctrine of the schematism, according to Heidegger. is a necessary and intrinsic part of Kant's view of man, for the transcendental faculty of imagination is the basic unifying power in our knowledge. This faculty represents the underlying unity of what Kant calls sensibility, understanding and reason. Thus, time and finitude pervade all of experience and -- consequently -- all of being. Kant had seen that temporality is even more basic to experience and being than is spatiality, and thus he was groping toward the insights into being and time that Heidegger was formulate more than a century later.

This bold statement of the real meaning of Kant became the source of a good deal of controversy -- although the "anthropological accent" in Kant's work has been recognized by various other scholars. In 1931 Ernst Cassirer published an important review article on Heidegger's book in Kant-Studien. He acknowledged the philosophical profundity of Heidegger's book and agreed with some of the points made, but he rejected Heidegger's reading of Kant as a distortion both of what Kant said and of what he intended. He pointed out that Heidegger virtually makes Being and Time (1927) a presupposition for understanding Kant's Critique of Pure Reason (1781). Kant's problem, Cassirer declared, "... is not the problem of being and time but rather the problem of `is' and `ought,' of experience and Idea." [NOTE 20] When Heidegger combines sensibility and reason in the notion of "sensuous reason," Cassirer went on to say, he "... no longer speaks as a commentator but as usurper, who penetrates, as it were, by force of arms into the Kantian system in order to subdue it and make it serviceable for his problem." [NOTE 21] But is Heidegger really a usurper? Just what is the difference between a commentator and a usurper? We will return briefly to this question in the concluding section.

Kant as Idealist

As we have seen, many of the philosophers of the nineteenth and twentieth centuries have claimed Kant's mantle. If we are to reach a decision about the real meaning of Kant and about who is really carrying on Kant's work, the neo-Kantians obviously deserve serious consideration. The members of the Marburg school of neo-Kantianism (not to be confused with the Baden school, represented chiefly by Wilhelm Windelband and Heinrich Rickert) not only speak in the name of Kant but have produced various significant works on Kantian epistemology and Kant's own writings. The chief representatives of the Marburg school, i.e. Hermann Cohen (1842-1918), Paul Natorp (1854-1924), and Ernst Cassirer (1874-1945), therefore merit some attention in our effort to get at the real meaning of Kant.

The first thing to notice about the version of Kant presented by these Marburg neo-Kantians is that it makes Kant an epistemologist. Although the charge of metaphysics has been raised against them, they deny the possibility of metaphysical knowledge and claim fidelity to Kant on this point. But in their epistemological reading of Kant, they remove his thought from the context of the debate between rationalism and empiricism. Kant is not to be regarded as a synthesis of rationalism and empiricism, they claim, but as an antithesis of both, for he denied that knowledge is in any sense a mirroring of realities or entities outside consciousness (the common ground in the debate between rationalism and empiricism). Our knowledge is at bottom not a mirroring or a reproducing or a reconstructing but a producing (erzeugen). This doctrine of knowledge entails a denial of receptivity of "the given" in the process of knowledge. Hermann Cohen, describing his own neo-Kantian concept of knowledge, insisted that it is a mistake to suppose "... that thought is given its material from sensations and that thought has only to arrange this material." Nothing can be given to thought which does not arise out of thought. According to Cohen, "Only thought itself can produce that which is to count as being." [NOTE 22] In short, being is a function or product of thought.

This idealist statement of the relationship between thought and being has obvious consequences for how the celebrated categories are to be understood. A.J. de Sopper, whose excellent introduction to philosophy (entitled Wat is philosophie?) includes an illuminating discussion of Kant and neo-Kantianism, summarizes these consequences as follows: "The categories are not copies within consciousness of a reality outside consciousness, as various types of realism teach. Neither are they psychical capacities or properties of man, by means of which our picture of reality is falsified through subjective admixtures, as one line of criticism based on misunderstanding teaches. In that case they would only have constitutive significance for the coming about of a phenomenal world of experience. No, the categories have creative significance for the only true reality, the reality produced by thought. We do not get objective knowledge when thought mirrors -- either in an adequate or an inadequate manner -- something standing over against it, a reality independent of it, but only when thought produces (erzeugt) in the proper manner. In the whole of this thinking there is place neither for the thing-in-itself nor for metaphysics." [NOTE 23]

But if these Marburg neo-Kantians are to be interpreters of Kant and philosophers faithful to the spirit of Kant, what are they to make of the doctrine of the thing-in-itself, which is mentioned so frequently in the Critique of Pure Reason? Fortunately, they were far enough removed in time from Reinhold to be able to avoid repeating his error. Because thought receives no matter originating outside itself, they could not maintain that the thing-in-itself is the ultimate origin of the matter of sensation. Nonetheless, they did find a place for the thing-in-itself in their statement of the real meaning of Kant's philosophy, a place which (on their reading) accords with various passages in the Critique of Pure Reason. Kant himself had declared that "The concept of a noumenon is thus a merely limiting concept, the function of which is to curb the pretensions of sensibility; and it is therefore only of negative employment." [B311] But in the Critique Kant does not speak of the noumenon or the thing-in-itself only as a limiting concept. Ernst Cassirer has an explanation for this: "... it is characteristic of the critique of reason that it does not present the conditions on which all knowledge depends as a finished whole at the outset, but rather that in its own gradual progress it first gains and works them out. Therefore, its new concept of knowledge cannot at any stage of exposition be exhibited and isolated as completely finished; rather, it first becomes clear when one keeps in mind the essence of all the individual logical steps. To the various stages on the way to the critical concept of objectivity, there must necessarily correspond an equally varied series of formulations of the concept of the thing-in-itself. This concept represents nothing more than the limit on our empirical knowledge, the horizon which encloses the field of vision of our experience. Consequently, it displays various sides in accordance both with the field of vision itself and with the concepts given in it. Because of these factors, the problem takes on that peculiar, complicated form which gives rise to the struggle of interpretations." [NOTE 24]

The thing-in-itself, understood as a limit on our knowledge and an ever-receding horizon, must nonetheless be understood in relation to the given -- but not in the way usually ascribed to Kant. De Sopper summarizes Cassirer's thinking on this point as follows: "For philosophy, the so-called given reality is the eternally unknown. The `thing-in-itself' here is not the symbol for the underived character of the given but for the unending task for scientific thought ...." [NOTE 25] The real object of philosophical thought, therefore, is not the world or the totality of being as such but reality as known by us (i.e. produced in thought). In other words, philosophy's object is the world as known through scientific thought and cultural forms -- hence Cassirer's emphasis on philosophy of science (an emphasis shared with the positivist tradition) and philosophy of culture (a virtual unknown in the positivist tradition).

For the Marburg neo-Kantians with the postulated identity of thought and being, idealism represents the real meaning of Kant. Although their own conception of knowledge is not an interpretation of Kant in the strict sense, they do regard it as a fulfillment of the most promising line of thought in Kant's philosophy.

Understanding, Interpretation and Evaluation.

It is not my intention in this concluding section to render a decision on which of the "real meanings" of Kant is really the real meaning of Kant. Such a decision would involve more than just an appeal to the text, for if such an appeal were sufficient to decide the question, we could refer the entire problem to a "Kant expert," one of the many scholars who have made a career of studying Kant. Most of these Kant experts have devoted considerably more time and energy to the study of Kant than have the philosophers whose views of Kant were discussed above. Why, in that case, do we focus attention on these philosophers rather than on the Kant commentators?

Kant's Critique of Pure Reason is almost universally regarded as a work of philosophical genius. The philosophers discussed above, including those who are strongly critical of Kant, entertain a very high opinion of Kant's significance for philosophy. Now, if Kant is so dreadfully important, what does it mean to understand his work? Would we say that someone had grasped the Critique if he had memorized it and could repeat it word for word? Obviously not. What about someone who could paraphrase the major sections? This would be a beginning, but would hardly count as a profound understanding of Kant. What about someone who could give a fairly brief summary of the Critique or the critical philosophy -- such as one finds in many histories of philosophy -- and could answer questions about the summary? This would be better yet, but would still fall short of a profound understanding -- although it would probably suffice for a doctoral qualifying examination on the history of philosophy. A truly profound understanding of Kant would require an intimate acquaintance not only with what Kant said but with his problems. For this reason, no one is better equipped to understand what a great philosopher has achieved than another philosopher. (I am assuming that not everyone who holds an advanced university degree in philosophy counts as a philosopher in the strict sense.)

For a philosopher to understand Kant, then, he must make Kant's problems his own. Only when he has himself wrestled with Kant's problems will he be in a position to grasp Kant's doctrines in their full significance, i.e. as answers to real problems. This is only another way of expressing the truth that a philosophical understanding and interpretation of a philosophical text is more than a meeting between two minds. Because philosophical discourse is about something (i.e. the world, or being, of human knowledge, or eternal puzzles), it must always be understood in relation to that which it is about. (The same is true, obviously, for other kinds of discourse.) Students of Hegel's Logic sometimes complain that they literally have no idea what in the world Hegel is talking about, and consequently they can make little sense of him. If Hegel was only engaged in a gigantic thought-experiment (as Kierkegaard suggested), then we would have to understand and judge his philosophical results in a way different from that used for others philosophers.

The philosopher who wants to understand Kant as philosopher must determine what Kant is talking about. Is he telling us what knowledge is, or what objects are, or what man is, or something so new and different that it is beyond comprehension? In other words, he must view what Kant has written as an answer to some basic question or set of questions. Once he has taken this step, his understanding of Kant has become an interpretation. Furthermore, by that point he has brought Kant into his own philosophical universe. In The World as Will and Representation, to take an example, Schopenhauer views Kant's work as a set of good answers (but somewhat inadequately formulated) to what he (i.e. Schopenhauer) takes to be the real problems of philosophy. The real meaning of Kant -- for Schopenhauer and for any other philosopher -- thus lies in the answers he has given to the real problems of philosophy, and the prior philosophical decision as to what the "real problems" are becomes the basis for the separation of "kernel" and "husk" in Kant's writings.

Once an interpretation of Kant is related directly to the "real problems" of philosophy, it also becomes an evaluation. As we have seen, each of the views of the real meaning of Kant presented above contains its own implicit -- and sometimes explicit -- evaluation of Kant. On the level of true philosophic discussion and interchange -- which must be distinguished from pedagogical interchange and from basic scholarship ancillary to philosophical investigation -- understanding, interpretation and evaluation are inseparably intertwined.

To return to Cassirer's charge against Heidegger, the latter is indeed a usurper, but only from the standpoint of Cassirer's own philosophical position. As Cassirer is well aware and freely admits, Heidegger's reading of Kant is itself a piece of philosophy and can only be understood and evaluated on the basis of Being and Time. In other words, Heidegger's version of the real meaning of Kant is logically dependent on what he establishes -- or tries to establish -- about being in his own systematic philosophical works.

If this long and somewhat tedious story has a pedagogical moral, it is that insight into the thinking of major figures in the history of philosophy cannot be achieved apart from insight into the problems of philosophy. Therefore it is a mistake to suppose that "history of philosophy" can be learned in isolation from or before "systematic philosophy." The real meaning of Kant must be sought in relation to "systematic philosophy" and its problems -- and not by inquiring into Kant's influence on other philosophers, on German literature and history, on theological thought, or by investigating his relation to previous thinkers. These questions are certainly interesting in themselves, but in a philosophical context they are secondary.

In short, the real meaning of Kant will never be discovered by someone who spends all his time reading Kant's works -- any more than the real meaning of the Scriptures will be discovered by someone who spends every spare moment reading and re-reading the Bible. Only when we ourselves reflect philosophically on that which Kant was talking about will we have any hope of achieving a deep understanding of his work. As students of the Hegel literature are well aware, interpretations of a great philosopher that are profoundly wrong are often much more stimulating and useful than re-statements and paraphrases that are formally and terminologically faithful to the philosopher in question.

Theodore Plantinga
November 1972


[NOTE 1]
Kleist, Briefe (Vol. 5 of his Werke), ed. Erich Schmidt (Leipzig and Vienna: Bibliographisches Institut, no date), p. 204.

[NOTE 2]
Ibid, p. 207.

[NOTE 3]
Cassirer, Das Erkenntnisproblem, Vol. III, p. 37.

[NOTE 4]
Quoted by Cassirer, op. cit., p. 127.

[NOTE 5]
Kroner, Von Kant bis Hegel, Vol. I, p. 55.

[NOTE 6]
Ibid., p. 58.

[NOTE 7]
Ibid., p. 60.

[NOTE 8]
Quoted by Kroner, op. cit., p. 362.

[NOTE 9]
"Criticism of the Kantian Philosophy," p. 424.

[NOTE 10]
Ibid., pp. 417-18.

[NOTE 11]
Ibid., pp. 419-20.

[NOTE 12]
Ibid., p. 434.

[NOTE 13]
The Philosophy of "As If," p. xxvii.

[NOTE 14]
Ibid., p. xlii.

[NOTE 15]
Dooyeweerd, A New Critique of Theoretical Thought, Vol. I, p. 357.

[NOTE 16]
See Kern, Husserl und Kant, pp. 4-5.

[NOTE 17]
Ibid., p. 41.

[NOTE 18]
Heidegger, Kant and the Problem of Metaphysics, p. 207.

[NOTE 19]
Ibid., p. 217.

[NOTE 20]
Cassirer, "Kant and the Problem of Metaphysics," p. 148.

[NOTE 21]
Ibid., p. 149.

[NOTE 22]
Quoted by de Sopper, Wat is philosophie?, p. 126.

[NOTE 23]
Ibid., pp. 126-7.

[NOTE 24]
Cassirer, Das Erkenntnisproblem, Vol. II, pp. 741-2.

[NOTE 25]
De Sopper, op. cit., p. 129.


Cassirer, Ernst. "Kant and the Problem of Metaphysics" (first published in German in Kant-Studien in 1931), in Kant: Disputed Questions, ed. Moltke S. Gram. Chicago: Quadrangle Books, 1967, pp. 131-157.

Cassirer, Ernst. Das Erkenntnisproblem in der Philosophie und Wissenschaft der neueren Zeit, Vols. II and III. Darmstadt: Wissenschaftliche Buchgesellschaft, 1971.

Dooyeweerd, Herman. A New Critique of Theoretical Thought, Vol. I: The Necessary Presuppositions of Philosophy, tr. David H. Freeman and William S. Young. Philadelphia: Presbyterian and Reformed Publishing Company, 1953.

Hartmann, Nicolai. Die Philosophie des deutschen Idealismus, Vol. I: Fichte, Schelling und die Romantik. Berlin: Walter de Gruyter, 1960.

Heidegger, Martin. Kant and the Problem of Metaphysics, tr. James S. Churchill. Bloomington and London: Indiana University Press, 1962.

Kern, Iso. Husserl und Kant: Eine Untersuching über Husserls Verhältnis zu Kant und zum Neukantianismus. The Hague: Martinus Nijhoff, 1964.

Kroner, Richard. Von Kant bis Hegel, Vol. I. Tübingen: J.C.B. Mohr (Paul Siebeck), 1961.

Louet-Feisser, J.J. "Kant without End? The Critique of Kant in the Work of Dooyeweerd," in Philosophy and Christianity: Philosophical Essays Dedicated to Professor Dr. Herman Dooyeweerd. Amsterdam: North-Holland Publishing Company, 1965, pp. 212-219.

Schopenhauer, Arthur. "Criticism of the Kantian Philosophy," in The World as Will and Representation, Vol. I, tr. E.F.J. Payne. New York: Dover Publications, 1966, pp. 413-534.

De Sopper, A.J. Wat is philosophie? ("Volksuniversiteitsbibliotheek"). Haarlem: De Erven F. Bohn, 1950.

Vaihinger, Hans. The Philosophy of "As If": A System of the Theoretical, Practical and Religious Fictions of Mankind, tr. C.K. Ogden. London: Routledge and Kegan Paul, 1935.