https://doi.org/10.53656/phil2025-03-03

2025/3, стр. 292 - 307

CONCERNING THE NOUMENON, OR KANT’S THIRTEENTH AND FATAL CONCEPT OF THE TRANSCENDENTAL ANALYTIC

Резюме: The paper provides a detailed reconstruction of Kant’s deduction of the concept noumenon at the end of CPR’s Transcendental analytic with the final aim to undermine the view of its unknowability. According to our initial premise, the contradictions, faced by Kant’s transcendental idealism, have their origin on the systematic level. The noumenon should, therefore, be understood as a purely methodological entity with reality solely within the system of transcendental idealism or as a “conceptual gate,” that functions as system’s entrance and exit and preserves its connection with its philosophical “other” – the realism.

Ключови думи: Kant; transcendental idealism; noumenon; system; method

Introduction

This article addresses one of the most intriguing and, accordingly, most extensively examined topics within Kantian philosophy, namely – that of the noumenon. Despite its status as a well-trodden and problematized subject, the doctrine’s significance in the historical and philosophical aftermath of Kant’s thought, along with the potential for its reinterpretation to yield a novel perspective on transcendental idealism, provides a compelling rationale for revisiting this ostensibly unoriginal theme.

According to our initial hypothesis, knowledge of the noumenon is possible and even necessary for us to know anything within the framework of critical philosophy. The underlying intuition here is that it is a pure concept of understanding, which occupies a unique place within the Tables of pure and schematized categories and, in a specific sense, is more crucial than any of them for knowledge. This thirteenth pure concept is further defined as fatal for Kant’s critical project, insofar as it leads the system into a deadlock and, subsequently, to its sublation in absolute idealism.

To justify the provocative hypothesis concerning the knowability of the noumenon, one must begin by accepting Kant’s narrowest formulation of the term in the Critique of Pure Reason (1781; 1787), namely – as a concept, and more precisely, as a methodological concept operating within the system of pure speculative reason. In other words, from the very beginning we have to bracket not only Kant’s ontological assumptions, but also the problems related to the correspondence between knowledge and reality, as well as the possible solutions to these problems. This study, therefore, confines itself to the meta-concept noumenon, understood as distinct from and not synonymous with the “thing-in-itself,” which properly belongs to the domain of ontology. In justification of this restriction, it should suce to note that it aligns fully with Kant’s own use of the concept in the First Critique.

The hypothesis behind this abstraction from ontology is that the contradictions and problems in Kant’s view of reality are rather a superstructure over – that is, secondary to – the fundamental epistemological diculties that the German philosopher is facing in the process of constructing his philosophical system. The potential success of the present project would serve as an additional argument in favor of this intuition.

A natural additional limitation of the object of study, in accordance with the spirit of Kantian philosophy, is the restriction to theoretical and speculative philosophy, with the consequent bracketing of its practical consequences. According to the critical idealism, the practical “begins” where the discursive knowledge “ends.” Nevertheless, this reduction of practical issues as falling beyond the narrowly understood subject of investigation here does not hinder but, on the contrary, encourages a subsequent inquiry into the practical implications of the reinterpretation of the noumenon.

Our guiding questions will be those concerning (1) the nature, (2) the origin, (3) the function, and (4) the legitimacy of the concept of the noumenon. This will make it possible to further distinguish it from other transcendental units of the system, and most notably from the ideas of reason and the categories of the understanding. In this sense, this is a deduction of the pure concept of the noumenon – justification of the legitimacy of its use and an attempt to provide a positive answer to the transcendental questions of whether it constitutively enables knowledge and whether we have genuine knowledge of it. The goal is to develop an alternative perspective on the problems of Kantian philosophy, as well as an insight into their possible resolution.

Types of Representations

In The Critique of Pure Reason (A320/B376-77) Kant distinguishes between conscious and unconscious representations, with the conscious ones further divided into subjective (sensation) and objective (intuition and concept). Sensation is the matter of appearance, space and time are the forms of intuition, and the categories are the pure concepts of the understanding. Concepts are divided into pure and empirical, the latter being formed from the former through the addition of intuition.

Within the group of concepts, we could also include the transcendental ideas of reason (the soul, the world as a totality, and the Absolute Being), but only with the restriction that no intuition can be provided for them. That is, they are rather pseudoconcepts – they imitate concepts in form but do not fulfill the same function, since we have no access to the concrete and determinate content that could actualize them.

When we ask about the “place” of the noumenon within this general framework, there are, of course, two options: it is either a pure concept of the understanding or an idea of the reason. The reasons for excluding the other types of representations are as follows:

1. We cannot classify the noumenon as an unconscious representation, since we consciously refer to it as marking the boundary of knowledge.

2. It cannot be a subjective representation or a sensation, as, by definition, we cannot be affected by its referent in space and time.

3. For the same reason as (2), the noumenon cannot be a pure or empirical in

4. Since we cannot have intuition of its referent (3), it is impossible to construct it as an empirical concept.

In order to answer the question of whether the noumenon is a pure concept of the understanding or an idea of reason1 we need to trace back and evaluate the outcome of the deduction of this concept. This attempt is undertaken at the conclusion of the Transcendental Analytic, specifically in the chapter that Robert Wolff refers to as the “limiting chapter”2 – On the Ground of the Distinction of All Objects in General into Phaenomena and Noumena. We will now proceed with an analysis of this chapter.

Deduction of the Noumenon

Like any other concept, the concept of noumenon must be considered in two senses:

With regard to the object it refers to (synthesis) and

With regard to the act of referring itself (analysis).

When it comes to the entity designated by the concept (1), we indeed cannot speak of the knowability of noumenon’s ontological correlate, although we can think of its “transcendental object = x.”3 With regard to the noumenon as a designator, however, a decisive negative answer is not possible, since such a designator is surely conceivable. We do in fact predicate certain properties of the noumenon as a referring term, for we legitimately arm certain qualities of its referent, even if the latter is understood only in its purely methodological sense as the boundary of knowledge. In this regard, bracketing out its ontological reality does not entail a complete loss of reality, insofar as the noumenon, as a meta-concept, retains an immanent, intra-systemic reality within transcendental idealism – a point to which we will return later.

On the basis of Kant’s explicit statements in the chapter On the Ground of the Distinction of All Objects in General into Phaenomena and Noumena, we are justified in asserting the following:

1. Regarding the origin of the representation, noumenon is an intellectual concept of pure understanding, by which the thing-in-itself must be thought (A24849; A254-56/B310-12). It is a pure concept of the understanding, insofar as it expresses the form of thinking (A252; A254/B309) – it determines a certain object for the manifold of a possible intuition (A254/B309).

2. The object of noumenon is the genuine, intelligible object (the thing-in-itself) as opposed to all phenomena (A249; A252; A257/B313; A259; B315). Hence, the concept has a dual meaning:

2.1. Noumenon in the negative sense refers to the object of an indeterminate non-sensible intuition (A252; B307; A254-56/B310-12) (an epistemological boundary).

2.2. Noumenon in the positive sense refers to the object of an intellectual intuition (B307) (an ontological idea).

3. By its nature, noumenon is a problematic concept (A254-56/B310-12; A25960/B315), and its bearer (the understanding) is itself a problem (A256/B311). This problematic status stems from the internal tension between its twofold meanings, as well as from the observation that it possesses both legitimating and delegitimating properties, namely:

3.1. Definability. The concept can be analyzed because:

3.1.1. It is logically possible, as it does not contain a contradiction (A252; A25456/B310-12).

3.1.2. It has purposefulness, as it is not an arbitrarily invented concept.

1.1.3 It has functionality, as it is necessary and inevitable for delimiting the validity of knowledge.

3.1.4. It has systematic connectedness, as it stands in relation to other forms of knowledge (A254-56/B310-12).

3.2. Contentlessness. Its synthesis (schematization) is impossible because:

3.2.1. It lacks objective validity, as it has no determinate referent.

3.2.2. Its objective reality is unknowable (A254-56/B310-12).

4. With regard to its function in the system, noumenon is a boundary concept (A254-56, B310-12) – an empty space(ein leerer Raum) (A259-60/B315), that limits the objective validity of sensible knowledge as a whole (A254-56/B310-12) and empirical principles in particular (A259-60/B315).

5. Finally, the domain of noumenon is defined as beyond the unity of time (Zeiteinheit), and thus beyond any use and meaning of the categories (B308).

This deduction allows us to re-establish Kant’s fundamental conditions for a concept to be legitimate, namely:

1. It must be definable or analyzable (analysis).

2. It must designate or refer to a determined possible/actual object (synthesis).

According to the critical method, these two conditions correspond respectively to the logical possibility and objective validity of a concept. If it meets both, the noumenon is a pure concept of the understanding; if it meets only the first condition, it is an idea of reason.

At this point, it would be useful to emphasize some aspects of the presented deduction that may turn out to be crucial for the following reconstruction of the noumenon as a representation:

First, according to 3.2.1, the noumenon’s objective validity is denied, since its referent is indeterminate. Our strategy for arguing the knowability of the noumenon will involve a deeper analysis of the various levels and domains in which criteria for objective validity are satisfied within the system. Additionally, we will explore whether determinacy or concreteness necessarily requires an ontological referent of the concept. A particularly useful approach here would be to explore the possibility of a purely methodological or intra-systemic reality, which follows from the connectedness of the noumenon with other forms of knowledge (3.1.4) and its necessity within the system of knowledge (3.1.3).4

Second, the claims regarding the function (4) and domain (5) of noumenon examine it in relation to the forms of intuition, which creates an intriguing tension with Kant’s standard approach to pure representations. Why would a pure concept, which contains nothing from sensibility and is a product of the spontaneity of the understanding, require reference to pure intuitions in its definition?

An even more intriguing observation follows when we combine the two claims: Kant defines the noumenon as an “empty space beyond the unity of time.” On the one hand, from the Metaphysical Exposition, we know that empty space is still determined (i.e., finite) and is still space (A24/B38-39). On the other hand, every representation, being a representation of temporalizing consciousness, is always within time (A34/ B50-51). It is also problematic to claim that the noumenon exists in space but beyond time, since one of the key conclusions of the Transcendental Aesthetic is that a representation can be purely temporal, but never purely spatial (A34/B50-51).

Even if we assume that Kant is here treating the noumenon exoterically and metaphorically – a move arguably inconsistent with the established practice of transcendental deduction as a procedure – the question remains: why did he not opt for a more neutral term than “space,” such as “domain,” “field,” or “extension”?

Reason’s Ideas

Returning to the question of what type of representation the noumenon is, and in light of the deduction above, it would be quite natural to conclude that it is an idea of reason – a thought that, although being illegitimate in a constitutive for knowledge sense, refers to an essence that exists independently of our consciousness and (presumably) causes the appearance. In other words, a thought about the thing-initself to which this speculative thought refers. But before we rush to classify the noumenon under this title, let us first reflect on the following points:

First, the introduction and deduction of the concept occurs in the Transcendental Analytic, not in the Transcendental Dialectic. In view of the methodology and chronology of Kant’s Doctrine of Elements, this means that the noumenon is a pure concept of the understanding. Its deduction takes place at the end of the discussion of the understanding – that is, before the transition to the domain under the jurisdiction of reason in the narrower sense, and prior to the introduction of its transcendental ideas. If it were an idea, the deduction of the noumenon would have been positioned at the beginning of the Transcendental Dialectic.

Second, Kant explicitly defines the noumenon as a concept – and more specifically, as a boundary concept. The boundary makes possible and secures knowledge within that boundary; that is, this concept must be pure and function as a transcendental and constitutive condition for knowledge, just like the categories. Otherwise, we would fall into the contradiction of claiming that the boundary lies beyond itself.

Third, insofar as the noumenon is legitimized in the final chapter of the Transcendental Analytic by virtue of its role as a cognitive boundary, the deduction of this concept should be considered successful. Its function is not merely regulative but strictly constitutive, as it is originally necessitated by the system itself and therefore enables cognition from the outset. Accordingly, it does not represent a remote and unattainable ideal derived from existing knowledge, but rather a foundational condition that precedes and grounds the possibility of knowing.

From a substantive point of view, the main argument against identifying the noumenon as an idea of reason is that ideas refer to determined ontological entities that are unknowable (the immortality of the soul, the properties of the world as a totality, and the existence of the absolute being); whereas the referent of the noumenon, although defined, is not ontological but intra-systemic – namely, the boundary of cognition. In short, ideas concern unknowable but thinkable ontological entities, while the noumenon pertains to an object posited within the critical system – even if its knowability remains an open question at this stage. Its object, taken in its positive sense, is not actual being, and if we wish to attribute reality to it, this can only be intra-systemic reality – reality as part of the system of critical idealism. Thus, the specific thing the concept refers to is not, as in the case of ideas, on the level of things, but on the level of the system. Hence, as we intend to show, the noumenon, unlike the ideas, has knowable content in the experience of the transcendental Self with the system itself.

Understanding’s Pure Concepts

Turning to the last remaining alternative for classifying the noumenon as a representation, we must begin with the important distinction between (1) pure and (2) schematized categories. Strictly speaking, only schematized categories pertain to appearances, whereas the actual referent of any pure category cannot be pointed to in experience5 – precisely as in the case of the noumenon. By definition, a pure concept of the understanding does not refer directly to an object of sensuous experience; however, this does not entail that it lacks any referent whatsoever within the system of knowledge. At the same time, the referents of the pure category and of the noumenon are presupposed in every conceptual representation: the pure categories provide the order within the representation, while the noumenon grants it its realistic weight, as a thought of its referent beyond the limitations of the subject. Therefore, just as knowledge is impossible without unschematized categories, it is also impossible without the noumenon – both the pure categories and the noumenon originally make experience and knowledge possible. From this, we must conclude that whatever functional knowledge we have of the pure concepts of the understanding (even though they do not apply directly to appearances in empirical knowledge), we must similarly acknowledge some functional knowledge of the noumenon. The latter is, by definition, comparable to the pure categories and may therefore be regarded as the thirteenth pure concept of the understanding.

Although Kant doubts the legitimacy of the universal use of the pure concepts, he nevertheless makes efforts to preserve the possibility of such use, even if only as purely problematic.6 The reason for this is that such use is the stake of realism. Nevertheless, the doubt regarding the legitimacy of their universal applicability does not render any of these thirteen meta-concepts any less necessary for the possibility of knowledge.

***

The pure unschematized categories represent the pure thought of something, and this function aligns them with the concept of the noumenon. At the same time – and this is the decisive difference between them – the pure categories are rules of synthesis, i.e., they presuppose the presence of material to be synthesized, given by a source beyond the understanding. A category can perform its synthesizing and ordering function only on the assumption of something that can and must be synthesized, ordered, for it to become meaningful. It is in this sense that the doctrine of the Epigenesis of Pure Reason (B166-67) should be understood: the categories make experience possible, but the initial impetus for their synthesis arises precisely from the presence of a kind of experience with the world that actually transcends the understanding.

As for the noumenon – in neither of its two meanings does it function as something that synthesizes given material. In its negative meaning, the noumenon marks and refers to the boundary of knowledge; but this boundary is not the synthetic result of uniting the knowable and the unknowable, but rather what makes the distinction between their respective domains possible in the first place. In its positive meaning, the concept of the noumenon preserves the realist ground of representation within the critical project of transcendental idealism; but even this representation of the real, which underlies the appearance, is only possible within the critical distinction between knowledge and reality – that is, it is not synthesized into the concept but, on the contrary, breaks down into knowledge and an unknowable ontological reality within the process of building the system. In this sense, the knowledge we can speak of in relation to the noumenon is not discursive, as all conceptual knowledge based on categories is. This transcendental difference prevents us from identifying the noumenon with the categories, even despite their kinship as both belonging to the general class of pure concepts of the understanding.7

The Thirteenth Pure Concept

Kant is not in a position to restrict the use of the categories to their legitimate empirical field, insofar as the pure concepts of the understanding do not have their origin or grounding in sensibility. And yet, as rules of synthesis, the categories presuppose a certain material – given from beyond the understanding – that is to be synthesized.

The question that now arises is whether the concept of noumenon indeed fulfills this transcendental function – namely, that of enabling knowledge by marking a boundary against, and standing in dialectical opposition to, the unknowable. Despite contradicting their essential definition as rules of synthesis, this function is demanded of the pure categories. Furthermore, the necessity of such a transcendental use of the understanding is explicitly noted by Kant at the beginning of the “limiting chapter” in the Transcendental Analytic:

But there is one advantage, which can be made both comprehensible and interesting to even the dullest and most reluctant student of such transcendental investigation, namely this: That the understanding occupied merely with its empirical use, which does not reflect on the sources of its own cognition, may get along very well, but cannot accomplish one thing, namely, determining for itself the boundaries of its use and knowing what may lie within and what without its whole sphere; for to this end the deep inquiries that we have undertaken are requisite. But if the understanding cannot distinguish whether certain questions lie within its horizon or not, then it is never sure of its claims and its possession, but must always reckon on many embarrassing corrections when it continually oversteps the boundaries of its territory (as is unavoidable) and loses itself in delusion and deceptions. (А237-38/В297; emphasis added).

Justifying the critical system requires the limitation of knowledge; but for this, a boundary is needed, one that reason must have originally set for itself – that is, its transcendental use is necessary. Otherwise, both transcendental logic as a method and the very distinction between Transcendental Analytic and Transcendental Dialectic become impossible. The categories cannot fulfill this function, since they are rules of synthesis; therefore, this decisive move in the construction of the system can only be accomplished by the noumenon – the only remaining pure concept of the understanding.

If we follow this line of reasoning further, the concept of noumenon, taken in its strict sense, does not aim at expanding knowledge beyond the bounds of possible experience. It rather functions within the necessary program of the understanding’s self-regulation by indicating an “empty space” beyond empirical knowledge. Consequently, through this concept, the understanding questions itself, rather than what is “beyond” itself. The “beyond,” on the contrary, here marks the sensory material, insofar as the latter is precisely what the understanding receives from beyond itself. The noumenon, on the other hand, is a pure concept originally belonging to it.

The Boundary

Thus, speaking of the noumenon is not a stepping outside the realm of appearances and, as Kant would put it, “wandering in merely intelligible worlds,” but rather an examination of the boundary itself – one that must be possible as a procedure and is even required by the logic of the critical system. Experience as such becomes possible only through the categories8 – the demonstration of which, for Kant, is a justification of their objective validity (B168 – 69). And yet, only through the concept of noumenon is the critical system possible, because the Critique requires the meta-representation of a boundary. Therefore, this pure concept must also be granted objective validity.

The noumenon is a pure representation of the critical system not because the first Critique begins with the presupposition of the distinction between appearances and things-in-themselves – a distinction concerning the relation between epistemology and ontology. Rather, it is a pure representation because the system cannot be constructed at all without first postulating the boundary and the “empty space” beyond it, i.e., the noumenon in both its negative and positive senses. Therefore, the noumenon, in both of its meanings, responds to a fundamentally systematic and methodological – not ontological – need.

The particularity of this conceptual boundary of the system lies in the fact that through it, the critical system points beyond itself.9 But this can in no way be regarded as a purely regulative act – by pointing to the “empty space” beyond itself as a boundary, the noumenon determines not only what is internal to the system but also what is external to it. Even if the place is empty, the act of pointing to it outlines and assigns a role or a kind of significance to it. Thus, if time is the “front” side of the boundary between the knowable and the unknowable, then its “reverse” side would be precisely the noumenon – “beyond” time, but “within” the space of the system. In this sense, the noumenon-as-boundary must be understood as simultaneously presence and transcendence10 – as the intersection of constitutive law and the regulative awareness that the transcendental Self, beyond the system and its boundary, is the legislator.

Noumenon’s Objective Validity

To claim that the noumenon has a constitutive function for knowledge would mean to contradict what Kant explicitly states in the deduction of the concept – he insists that it lacks objective validity (A254 – 56/B310 – 12). At the same time – and this is the crucial point here – the requirement that the noumenon (as well as any category) fails to meet is the requirement for the objective validity of empirical, not pure, concepts, namely: to designate its actual ontological referent.11 The noumenon is expected to point out in our experience of the world a particular thing that serves as an example falling under the concept.12 But a transcendental concept within the critical system cannot meet this requirement for objective validity and reality – the pure concepts of the understanding are the methodological tools of the critical system itself, which is why, as we know from Kant, entirely different criteria are necessary for assessing their objective validity. For example, the pure unschematized categories possess objective validity not because their actual object can be “intuited,” but because they serve as the formal condition for constructing empirical concepts from the side of the understanding.

In short, the problem encountered in the attempt to deduce the concept of noumenon at the end of the Transcendental Analytic is precisely this: Kant treats it as a pure concept of the understanding but denies it objective validity because it does not meet the criteria for objective validity set for empirical concepts. However, if, in accordance with the logic of critical idealism, we attempt to seek its objective validity not on the empirical, but on the transcendental and systematic level, we would probably reach a different conclusion regarding its “fate.” The noumenon could be justified, for instance, as the only possible originally conceivable unity of the represented object as something independent of consciousness (reality; thing-in-itself) with the consciousness-dependent representation of it (ideality; appearance).13 Just as we already presuppose the use of categories in experience, in knowledge we already presuppose the noumenon as the objective determination of every representation – the representation that behind all representations there stands something that is beyond consciousness.

The problem of the synthesis and the objective validity of pure concepts ultimately comes down to what we mean by the term “object.” If the object is the concrete actual thing with which we have had sensory experience, then the noumenon cannot have an object. But its object could also be an element of the framework of the critical system itself – that is, a purely methodological unit of the system; and this seems to be precisely the case with the noumenon. It functions as an external, wrapping boundary of the system, paradoxically legitimizing the system itself as if from the outside.14

Objective validity of the noumenon can therefore be sought only in a functional or methodological, not in a substantial or ontological, interpretation of the concept. All meanings of the noumenon are explained as a function within experience;15 but not the empirical experience of the world, rather the transcendental experience with the critical system itself.

Knowledge and Reality

The noumenon is introduced by Kant as a boundary concept – a concept that limits cognitive claims to reality as it appears in space and time. The goal of the critical system is not only to refute speculative metaphysics by restricting knowledge to the ontology of appearances but also to overcome “problematic idealism” (B274), which either doubts (in the Cartesian sense) or denies (in the Berkeleyan sense) the existence of things-in-themselves – things existing outside and independently of consciousness.

The noumenon, however, emerges as Kant’s thirteenth fatal concept: though its introduction is necessitated by the system itself, it generates a contradiction that ultimately enables the transcendence of that very system. Yet in raising these considerations, our aim is not to reject transcendental idealism; on the contrary, we seek to acknowledge the originality and historical-philosophical significance of the noumenon as a distinctive methodological concept – one that potentially could preserve realism, or the reality independent of consciousness, within the system.

Kant was undoubtedly aware of the diculties that this attempt to maintain realism within the system entails; but also of the inevitability of the concept. The simultaneous limitation of knowledge and armation of the unknowability of its boundary is doomed to contradiction – it is an assumption of a boundary that lies beyond itself. By distinguishing the knowable from the unknowable, the critical system cannot meet the very criteria for knowledge that it establishes.

In this context, Kant addresses these issues with an intriguingly dismissive tone at the very end of the section On the Amphiboly of the Concepts of Reflection:

Before we leave the Transcendental Analytic behind, we must add something that, although not in itself especially indispensable, nevertheless may seem requisite for the completeness of the system. The highest concept with which one is accustomed to begin a transcendental philosophy is usually the division between the possible and the impossible. But since every division presupposes a concept that is to be divided, a still higher one must be given, and this is the concept of an object in general (taken problematically, leaving undecided whether it is something or nothing). Since the categories are the only concepts that relate to objects in general, the distinction of whether an object is something or nothing must proceed in accordance with the order and guidance of the categories. (А290/В346)

The question of the archetypal generic concept, which Kant downplays here, can in a certain sense be regarded as the turning point in the history of transcendental idealism. In other words, the problem is not the dualism of the phenomenal and the noumenal as such, but rather the fact that the system cannot be realized without presupposing a boundary that precedes both them and the system itself, along with the dialectic inherent to that boundary. This is the inevitable contradiction of the critical method with itself, which leads to the disintegration of the system not due to external critique, but under the weight of its own structure.

Noumenon is an epistemological concept that is born out of an epistemological need.16 According to the requirements of critical philosophy itself, for there to be knowledge, reality must be presupposed as something independent of consciousness; otherwise, one falls into absolute idealism.17 In both of its meanings, the noumenon provides meaning and significance – realism – to the system as if from outside of it; but this means that the concept must possess objective validity, since it is a necessary condition for knowledge.

Conclusion

In what is likely his most famous and influential critique of German idealism, Friedrich Jacobi (1743 – 1819) contends that the central diculty he encountered with Kant’s transcendental idealism is this: without presupposing the thing-initself, one cannot enter the system at all, but with it, one cannot remain within it.18 If we are permitted to translate “thing-in-itself” as “noumenon,” we might agree with Jacobi’s statement, but not with his disappointment.

To sustain a critical system while resisting the seductive whirlpool of idealism is indeed a challenge – but it is precisely here that the dignity of Kant’s philosophy resides. The noumenon is neither an inaccessible boundary nor a truly external reality beyond the self. It is a methodological concept – a conceptual gate – that marks both the opening and closure of the system, enabling it to remain in relation to that from which it distinguishes itself. We may thus conclude that Kant – alone among the German systematists – opts to ground the system in a form of realism, thereby preserving, however fraught, the possibility of a way out and beyond idealism.

NOTES

1. Here we consciously exclude the possibility for the noumenon as a specific concept within the system to possess the unique status of being simultaneously a concept of the understanding and an idea of reason. The two meanings of the noumenon, which we are about to problematize, may indeed incline the reader to translate its epistemological functions into ontological language – that is, as two attributes of the same substance. But since Kant functionally distinguishes between the understanding and reason, and since we intend here to bracket ontological questions, this possibility will not be further examined; although, in a certain sense, it represents a further development of Kant’s own view and offers interesting speculative potential for overcoming the difficulties facing critical idealism.

2. Cf. Robert Wolff’s, Kant’s Theory of Mental Activity. A Commentary on the Transcendental Analytic of the “Critique of Pure Reason” (1963, p. 311).

3. For the relationship between the concepts of “noumenon” and “transcendental object,” see Kant, Critique of Pure Reason (1781; 1787): “The understanding accordingly bounds sensibility without thereby expanding its own field, and in warning sensibility not to presume to reach for things in themselves but solely for appearances it thinks of an object in itself, but only as a transcendental object, which is the cause of appearance (thus not itself appearance), and that cannot be thought of either as magnitude or as reality or as substance, etc. (since these concepts always require sensible forms in which they determine an object); it therefore remains completely unknown whether such an object is to be encountered within or without us, whether it would be canceled out along with sensibility or whether it would remain even if we took sensibility away. If we want to call this object a noumenon because the representation of it is nothing sensible, we are free to do so. But since we cannot apply any of our concepts of the understanding to it, this representation still remains empty for us, and serves for nothing but to designate the boundaries of our sensible cognition and leave open a space that we can fill up neither through possible experience nor through the pure understanding.” (A288 – 89/B344 – 45)

4. Intriguing is the relation between Kant’s position on the noumenon’s connection to other (genuine?) knowledge – despite the indeterminacy of its referent – and Hegel’s reading of the example of the hundred thalers (Hegel 1986, pp. 87 – 92). Here, however, we will limit ourselves to simply noting this connection.

5. In discussing the Analogies of Experience, Kant explicitly states: “the appearances must not be subsumed under the categories per se, but only under their schemata.” And continues: “For if the objects to which these principles were to be related were things in themselves, then it would be entirely impossible to cognize anything about them synthetically a priori. Now it is nothing but appearances whose complete cognition, to which in the end all a priori principles must come down to, is only possible experience, and consequently those principles can have as their goal nothing but the conditions of the unity of empirical cognition in the synthesis of the appearances; but these conditions are thought only in the schema of the pure concept of the understanding, and the category contains the function, unrestricted by any sensible condition, of their unity, as of a synthesis in general. These principles, therefore, justify us in compounding the appearances only in accord with an analogy with the logical and general unity of concepts, and hence in the principle itself we make use of the category, but in its execution (its application to appearances) we set its schema in its place, as the key to its use, or rather we set the latter alongside the former, as its restricting condition, under the name of its formula.” (A180 – 81/B223 – 24)

6. Cf. Kant, Critique of Pure Reason: “Thinking in itself, to be sure, is not a product of the senses, and to this extent is also not limited by them, but it is not on that account immediately of any independent and pure use, without assistance from sensibility, for it is in that case without an object. And one cannot call the noumenon such an object, for this signifies precisely the problematic concept of an object for an entirely different intuition and an entirely different understanding than our own, which is thus a problem itself. The concept of the noumenon is therefore not the concept of an object, but rather the problem, unavoidably connected with the limitation of our sensibility, of whether there may not be objects entirely exempt from the intuition of our sensibility, a question that can only be given the indeterminate answer that since sensible intuition does not pertain to all things without distinction room remains for more and other objects; they cannot therefore be absolutely denied, but in the absence of a determinate concept (for which no category is serviceable) they also cannot be asserted as objects for our understanding.” (A287 – 88/B343 – 44)

7. For the distinction between pure categories and the noumenon, but within an ontological reading of the doctrine, see the article by Markus Kohl, Kant on the Inapplicability of the Categories to Things in Themselves (Kohl 2015, pp. 90 – 114).

8. Cf. Kant, Prolegomena to Any Future Metaphysics (1783): “For the reader who is stuck in the long habit of taking experience to be a mere empirical combining of perceptions – and who therefore never even considered that it extends much further than these reach, that is, that it gives to empirical judgments universal validity and to do so requires a pure unity of the understanding that precedes a priori – I cannot adduce more here, these being prolegomena, except only to recommend: to heed well this distinction of experience from a mere aggregate of perceptions, and to judge the mode of proof from this standpoint.” (4:311)

9. Cf. the position of E. Hensby in Kant and Heidegger: The Place of Truth and the Shrinking Back of the Noumena (Hensby 2021, pp. 1507 – 24).

10. Cf. Richard Grabau’s reading of the thing-in-itself and the noumenon in the article Kant’s Concept of the Thing in Itself: An Interpretation (Grabau 1963, p. 776).

11. Cf. Kant, Critique of Pure Reason: “In the end, however, we have no insight into the possibility of such noumena, and the domain outside of the sphere of appearances is empty (for us), i.e., we have an understanding that extends farther than sensibility problematically, but no intuition, indeed not even the concept of a possible intuition, through which objects outside of the field of sensibility could be given, and about which the understanding could be employed assertorically” (A255/B310, emphasis added)

12. Cf. Kant, Critique of Pure Reason: “The mistake that most obviously leads to this, and can certainly be excused though not justified, lies in this: that the use of the understanding, contrary to its vocation, is made transcendental, and the objects, i.e., possible intuitions, are made to conform themselves to concepts, but concepts are not made to conform themselves to possible intuitions (on which alone rests their objective validity).” (A289/B345)

13. For the unity of the appearance and the thing-in-itself as two aspects of the same thing, see Kant, Opus Postumum: “The latter [the collective unity of the manifold of intuition] is, a priori, as unconditional unity, the formal element of appearance, in contrast with the thing in itself = x, which is not itself a separate [absonderliches] object, but is only a particular relation (respectus) [Beziehung] in order to constitute oneself as object” (Ak. 22:43 – 44)

14. This is approximately the case also with the categories as methodological concepts, whose ontological referent cannot be specified, but which legitimize appearances from outside sensibility.

15. Cf. Richard Grabau’s article Kant’s Concept of the Thing in Itself: An Interpretation (Grabau 1963, pp. 775 – 76).

16. For a more detailed account of this reading of the doctrine, see Sadik Al-Azm’s essay Kant’s Conception of the Noumenon (Al-Azm 1968, pp. 516 – 20).

17. According to Robert Wolff’s influential work Kant’s Theory of Mental Activity, the critique of pure reason cannot even be stated without presupposing the existence of independently real entities (Wolff 1963, p. 312).

18. Cf. Jacobi’s supplement “On Transcendental Idealism” to David Hume on Faith, or Idealism and Realism, A dialogue (1787): “I must admit that I was held up not a little by this diculty in my study of the Kantian philosophy, so much so that for several years running I had to start from the beginning over and over again with the Critique of Pure Reason, because I was incessantly going astray on this point, viz. that without that presupposition I could not enter into the system, but with it I could not stay within it.” (Jacobi 1994, p. 336)

Acknowledgments & funding

This study is financed by the European Union-NextGenerationEU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project SUMMIT BG-RRP-2.004-0008-C01.

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