/ Kant on Inner Sensations and the Parity between Inner and Outer Sense


Does inner sense, like outer sense, provide inner sensations or, in other words, a sensory manifold of its own? Advocates of the disparity thesis on inner and outer sense claim that it does not. This interpretation, which is dominant in the preexisting literature, leads to several inconsistencies when applied to Kant’s doctrine of inner experience. Yet, while so, the parity thesis, which is the contrasting view, is also unable to provide a convincing interpretation of inner sensations. In this paper, I argue that this deadlock can be traced back to an inadequate understanding of inner sense shared by both sides. Drawing upon an analysis of the notion of obscure representations, I offer an alternative interpretation of inner sense with a special regard to self-affection, apprehension, and attention. From this basis, I will infer that outer sense delivers sensory content that is initially and intrinsically unaccompanied by phenomenal consciousness; inner sense contributes by endowing such content with phenomenal consciousness. Therefore, phenomenal qualities can be regarded as the sensory manifold of inner sense. This alternative interpretation solves the long-standing dispute concerning inner sensations and would further illuminate Kant’s notion of inner experience.

1. Introduction

Inner sense is indubitably a central topic in Kant’s Critique of Pure Reason (henceforth, Critique) since it is, as Norman Kemp Smith states, “inseparably bound up with all his main tenets” (1923: 295). Herbert James Paton, another major Kant interpreter from the early twentieth century, declares this doctrine to be “the most obscure and difficult part” in Kant (1946: 233). After nearly a century, little consensus has been achieved with respect to the nature and role of this faculty.

This paper seeks to clarify a substantial aspect of inner sense, specifically inner sensation. Contrary to the sensations provided by outer sense, Kant does not specify what sensations are provided by inner sense. Many commentators thus hold the view that inner sense does not have a manifold of sensations of its own, and this would constitute a disparity between inner and outer sense; in contrast, certain commentators believe the opposite (henceforth referred to as ‘disparity thesis’ and ‘parity thesis’, respectively). However, both sides face insurmountable difficulties, an issue that I believe can be traced back to a false understanding of inner sense that most views share, namely that outer sense provides sensory materials that are already phenomenally conscious, and inner sense merely reappropriates these materials and complements them with certain types of ingredients. Instead, I provide an alternative interpretation of inner sense, one that has a special relation to self-affection, apprehension, and attention: outer sense delivers sensory materials that are not intrinsically phenomenally conscious; inner sense accompanies these materials with phenomenal consciousness. As such, phenomenal qualities are the sought-after sensory manifold of inner sense (henceforth, ‘sensory inner manifold’). I then demonstrate how this interpretation overcomes the difficulties that have been encountered by the previous interpretations of inner sense. Finally, I examine how my interpretation is able to withstand some objections that might stem from this new position. In this analysis, I confine myself to the immediate empirical output of inner sense (i.e., inner sensations) and do not discuss topics pertaining to the form of inner sense, such as time and time determination.

The disparity and the parity thesis at issue are concerned merely with the immediate product of inner and outer sense—that is, inner and outer sensations (henceforth ‘narrow disparity’ and ‘narrow parity thesis’, respectively). In contrast, the broad disparity and the broad parity thesis are concerned with whether inner and outer experience—that is, empirical cognition of the self and that of the outer world—are analogous with regards to their nature and structure.[1] According to the broad disparity thesis, there are, in contrast with outer sense, no genuine empirical inner cognitions as there are no genuine mental objects in inner sense; the broad parity thesis maintains the opposite.[2] The broad disparity and the broad parity thesis involve various aspects of inner and outer empirical cognitions, among which inner and outer sensations are the most decisive (see Kraus 2019: §3.1). The narrow disparity and the narrow parity thesis can thus be seen, respectively, as arguments for the broad disparity and the broad parity thesis. As this paper advocates a narrow parity thesis, it can therefore be regarded as a partial defense of the broad parity thesis.

2. The Disparity Thesis

At the beginning of the Critique (A19–20/B33–34),[3] Kant provides a general account of sensibility, which is the faculty of passively receiving representations. By virtue of sensibility, the mind represents something through being affected by it rather than by actively thinking of it. Sensibility consists of a material and a formal aspect. Sensations comprise the matter of sensibility. Space and time, as the forms of sensibility, represent the ways in which these sensations are arranged and combined into intuitions (A20/B34).[4] Kant further divides sensibility into outer and inner sense. While outer sense represents spatial objects, inner sense represents the self and its inner states as objects (A38/B55). Inner states, as objects of inner sense, are all types of states that the subject can have, for instance, outer representations, thoughts, subjective feelings, and desires.[5] Kant does not restrict his general characterization of sensibility to outer sense. As this must apply to inner sense, inner sense, with regard to its nature, stands on par with outer sense. Since outer intuition contains, as its matter, a manifold of sensations that arise in outer affection (A20/B34) and serve as vehicles for representing outer objects, inner intuition must, analogously, also contain a manifold of sensations that serve as vehicles for representing inner appearances. Indeed, Kant explicitly mentions the manifold of inner sense (Anth 7:134, 141–142; B157n., 158; A138/B177; MAN 4:471), yet does not specify how to conceive of its nature. He also employs the terms “inner intuition” (A22/B37; A32–33/B49–50; B156–158, passim.) and “inner perception” (i.e., empirical inner intuition, see B68, 156) repeatedly, as if they are uncontroversial terms that were similar to their counterparts in outer sense.

However, many advocates of the disparity thesis are of the opinion that it is impossible to uphold the analogy between inner and outer sense.[6] According to them, the analogy fails in many respects, with the most decisive being the lack of sensory inner manifold—that is, sensations that are merely traceable to inner sense.[7] The arguments that underlie the different variants of this position can be sympathetically abstracted as follows:

  • P1. Inner sense does not deliver sensations of its own.
  • P2. Inner sense does not participate in producing the sensations of outer sense and the feelings of pleasure and displeasure.
  • C1. Inner sense does not generate any empirical matter at all (P1, P2).
  • P3. Outer sense generates outer sensations as its empirical matter.
  • C2. There is a disparity between inner sense and outer sense. (C1 and P3)

The first premise is presumably supported by Kant’s claim: “the proper material in it [inner intuition], with which we occupy our mind, consists in representations of outer senses” (B67; henceforth known as a ‘proper-material thesis’).[8] For disparity theorists, this means that while perceiving one’s inner states, all that one is aware of are sensations that stem from outer sense, such as colors, sounds, warmth, and tastes. These are “sensible data” that, after being processed by spontaneous acts of understanding, can depict outer objects (A169/B211; A175/B217). In terms of this claim, Kant is thought to preclude the possibility that inner sense generates sensations that are qualitatively distinct from outer sensations. Consequently, all sensory materials of inner intuitions do not stem from inner sense.

For many disparity theorists, the proper-material thesis at B67 is restricted to the epistemological context of the Critique. Indeed, the faculty of pleasure and displeasure also provides “proper material” for inner sense, since feelings of pleasure and displeasure are, as inner states, also objects of inner sense[9] and display distinct phenomenal qualities that contribute to the content of inner intuitions.[10] Thus, the proper-material thesis should be modified to read as follows: “The proper material in inner intuitions, with which we occupy our mind, consists in sensations of outer senses and feelings of pleasure and displeasure.”

The second premise aims to rule out any possibility that inner sense, while not generating sensations of its own, participates in delivering empirical matter that belongs to the other faculties of the mind. In other words, the premise precludes outer phenomenal experience and feelings from being generated with the participation of inner sense. Without this premise, inner sense could be still said to yield a sensory manifold (even if not a sensory manifold of its own).[11]

The second premise appears to be supported by strong reasoning. Most disparity theorists do not examine the possibility that inner sense participates in producing the sensory manifold of outer experience (henceforth as ‘sensory outer manifold’). Some of them draw the first conclusion from the first premise and a weaker version of the second, which does not involve outer sense (see Paton 1936b: 389; Allison 2004: 278). This neglect is probably supported by the proper-material thesis: if inner sense obtains its “proper material” from outer sense, it cannot be said to participate in generating such material. Moreover, since self-affection generates “inner perception of the [outer] manifold given in the subject beforehand” (B67), sensory outer manifold must be independent from self-affection.[12] The phenomenal experience of pleasure and displeasure also cannot be produced in cooperation with inner sense. In Anthropology from a Pragmatic Point of View, the sensations of “inward sense,” that is, feelings of pleasure and displeasure, are explicitly distinguished from those of inner sense (Anth 7:153). This differentiation occurs because, in contrast with the latter, they cannot be combined into object-related representations in any way (KU 5:206; B66).[13]

Assuming that they are correct, the first two premises exhaust all possible ways in which inner sense can provide a range of inner sensations in the context of Kant interpretation,[14] and the inference of the first conclusion on the basis of the first two premises would therefore be valid. The third premise is uncontroversial, for Kant often explicitly stated it (B155n., 161 and passim.). The inference from the first conclusion and the third premise to the final conclusion is also unproblematic when taking into account the meaning of ‘disparity.’ Among the three premises that bear the weight of the arguments, the first and the third are, as attested to by uncontroversial textual evidence, secure in their claims; the second premise is supported by seemingly strong reasoning. As such, at this point in the paper, the disparity thesis appears to be based on a solid argument.

3. The Problems

The disparity thesis, should it be taken as the correct interpretation, would lead to three serious interpretative difficulties. The first concerns direct counter-evidence; the other two involve implications of the disparity thesis for interpreting Kant’s conception of empirical self-cognition. I will address these issues below in turn.

Disparity theorists have to endorse an eliminative account of inner perceptions due to their denial of the sensory inner manifold. However, in contrast with this view, Kant not only frequently speaks of inner perception (A107, 368, 379; B68, 155–156) but also addresses two types of sensory manifold. At B161, he mentions the “unity of the synthesis of the manifold, outside or within us.” He even attributes features to the sensory inner manifold that distinguish it from the sensory outer manifold: “In it [the empirical doctrine of the soul] the manifold of inner observation can be separated only by mere division in thought and cannot then be held separate and recombined at will” (MAN 4:471; Anth 7:141–142).

The second difficulty concerns the nature of inner experience (i.e., empirical self-cognition). Kant employs the term “object of experience” generally in two senses. According to disparity theorists, there is no object of inner experience in either sense as there is no sensory inner manifold that would be analogous to a sensory outer manifold (Allison 2004: 278–279). The object of experience in the strict sense, or “the object itself,” is the “persistent” or the substance, in which changing accidents can inhere (A183/B227). Less controversially, no such objects can be represented in inner experience as no persistence can be discerned in inner representations (A107, 348ff.; A22/B37).[15] The object of experience, in a broader sense, includes, in addition to the substance, accidents. Accidents are “(positive) determinations” (V-Met/Schön 28:510, 638), “states” (Refl 17:579) of the substance, or, stated plainly, “particular ways for the substance to exist” (B229). For the current purpose, accidents could be roughly taken to be anything that can be positively predicated of a substance (A186–187/B229–230). According to disparity theorists, inner sense cannot represent anything that can be a determination of a substance due to the lack of specific inner sensations.[16] On the reading of some disparity theorists, inner intuitions are not “representations of itself”—that is, they are neither representations of the self itself nor representations of its determinations (Allison 2004: 279). Consequently, contrary to a judgment of outer sense (such as “the table is red”), neither concepts in a judgment of inner sense correspond to any sensible inner intuition (like the concept of the self and that of “seeing a screen” in the judgment, “I am seeing a screen”). Since the self is the unperceivable “transcendental object” of inner sense (Allison 2004: 280), inner experience merely represents that something (e.g., the “seeing a screen” in the example from before) “belongs” to such an unperceivable noumenal object (e.g., the “I” in the same example).[17]

In contrast to this interpretation, Kant repeatedly takes inner states, especially representational states, to be “object[s] of inner sense” (A22/B37; A34/B50; A38/B55; A371; KpV 5:66). Thoughts about inner states rest upon “intuitions of inner sense” (A443/B471). He even clearly states that the perceptions of inner states are “consciousness of oneself in terms of the determinations of one’s state” (A107, my italics). Similarly, he claims that through inner experience, “I am … conscious of the existence of my soul in time, which I can cognize only as an object of inner sense through the appearances constituting an inner state” (Prol 4:336, my italics). Therefore, pace Allison, Kant holds that inner sense produces perceptions of inner states, from which empirical representations of the self result. While the subject cannot cognize itself as an empirical substance, it nonetheless has, in a sense, empirical cognitions of itself in terms of having empirical cognitions of its states.[18]

The second difficulty is closely related to the third. If inner sense does not represent the self, the self cannot be construed as appearing to itself in inner experience. Accordingly, the transcendental distinction between the self as it appears to itself and the self as it is in itself would no longer be tenable (see Allison 2004: 283–284; Collins 1999: 114; Gardner 1999: 299–300). However, the doctrine of the ideality of self-representation by inner sense is, as a central tenet of Kant’s critical philosophy, accentuated in various crucial passages of the Critique and other writings.[19] A proper understanding of Kant’s doctrine of inner sense thus has to be able to effectively accommodate this type of ideality.

4. Current Solutions

Disparity theorists have attempted to substantiate their position in different ways. Some suggest that the contribution of inner sense lies wholly in framing outer representations in a temporal dimension.[20] Through inner sense, representations ‘appear’ to occur in temporal succession and stand in various temporal relationships with one another. This temporal manifold, that is, various temporal durations and relations, is thus taken to be the manifold of inner sense (Kraus 2019: §3.1). This conclusion is favorable to disparity theorists: inner sense does not stand on par with outer sense as the latter provides not only a pure but also a sensory manifold; at the same time, the aforementioned problems that result from a lack of a sensory inner manifold can be mitigated, as the temporal manifold can be viewed as a kind of phenomenal quality and thus represents how inner states appear to us.

Kant’s articulations, and, in particular, one passage at B154, do sometimes arouse the impression that temporal awareness constitutes everything that inner sense can deliver (see also Refl 18:312; Refl 18:314–315). These passages are nevertheless misleading, partially because Kant also asserts that relations exhaust what outer sense provides (B67), which is obviously not the whole story as outer sense also effectuates sensations.[21] Additionally, crucial textual evidence indicates that temporal awareness is only the formal aspect of inner sense and does not exhaust what it can provide (B67–68). In my view, even if one ignores this complication, disparity theorists would still face an insurmountable difficulty: what precisely does it mean that mental states appear temporal? As temporality is a formal character of inner appearance (B50, 224), how could we meaningfully assert that a mental item appears temporal, even if there are no specific sensory materials that could be employed to represent this very item?[22]

The second approach defends the disparity thesis by deflating the concept of inner intuition. Resting on the basis of an analysis of the crucial passages on self-affection (B68–69, 158–159), Friederike Schmitz (2015) denies that Kant is committed to a notion of inner intuition of the self or its inner states. She offers a novel interpretation of inner intuition: An intuition is an inner intuition if and only if it is provided by inner sense (Schmitz 2015: 1056). Inner sense has the role of delivering “temporally ordered outer intuitions.” Consequently, outer sensations are the output materials of inner sense and constitute its material aspect. Schmitz claims that in the Critique, Kant does not speak of “innere Anschauungen” but only of “innere Anschauung” (Schmitz 2015: 1057). Accordingly, there are no genuine inner intuitions that represent inner phenomena but only ‘inner intuiting,’ which is the process of producing outer intuitions through inner sense (Schmitz 2015: 1056–1058). Both this process and the outer intuitions propagated are related to the self and can be taken as ‘inner intuiting’ and ‘inner intuitions,’ because “the subject of cognition, by being conscious of an intuition which is due to its own act of combination, can cognize itself as the responsible faculty of combination and therefore as the subject of the respective intuition which it can accordingly attribute to itself” (Schmitz 2015: 1054–1055). In other words, outer intuitions, as a product of inner sense, are related to the self, as “by means of [these outer intuitions] an empirical self-consciousness of oneself as a subject to which those intuitions belong is made possible” (Schmitz 2015: 1052, 1054).

While intricate, Schmitz’s interpretation faces many difficulties. According to her, outer intuitions could simultaneously be classified as inner intuitions, which makes this distinction trivial and also contravenes textual evidence (A372, 378, 386; VAKpV 23:69). Moreover, pace Schmitz, Kant frequently speaks of “innere Anschauungen” (B471; KU 5:314; Br 13:472; Refl 15:216; Refl 17:637; VAKpV 23:69). If there were no genuine inner intuitions whatsoever, then Kant’s recurrent mention of “inner appearance” would not be able to be explained (A107, 386; A478/B506; A492/520; A673/B701; A690/B718; A771/B799; Anth 7:144, 399; Br 10:134).

Indeed, if Schmitz’s deflationary view were true, then according to Kant’s dichotomy of cognitive faculties in understanding and sensibility, the empirical self-consciousness based on outer intuitions could only be empirical (self-)thoughts rather than (self-)intuitions. In these thoughts, outer intuitions would then be taken as ‘belonging to’ the subject (Schmitz 2015: 1052, 1054). However, these intuitions do not refer to any inner phenomena themselves and hence cannot be sensible representations of the self. Consequently, Schmitz’s position still faces the second and third difficulty mentioned in the last chapter.

While disparity theorists are confronted by an irremediable situation, attempts in the opposite direction will find a similarly bleak outlook. Parity theorists have yet to be able to offer a satisfying notion regarding the sensory materials for inner sense. In analyzing Kant’s illustration of self-affection, in which the subject introspects the act of drawing a line in thought, Georg Mohr indicates that understanding’s spontaneous acts of spatial construction would be what effectuates sensory materials for inner sense.[23] The subject can perceive the mental acts of drawing a line by inward attention. As far as I know, Kant does not mention anything that can be defined as the sensory qualities of synthetical acts in the Critique nor in his other writings. Even if there were any such qualities, the most we could be able to infer from this illustration would be that we could perceive some sensory qualities of synthetical acts in introspection. Indeed, inner sense is affected not merely in introspection but is also “incessantly” in every conscious state (Refl 17:594; V-Lo/Blomberg 24:40; A155/B194; A177/B220). Thus, conclusions drawn from introspection cannot be extended to inner sense without further justification. Moreover, it is highly doubtful whether such justification is possible as introspection is an unusual case of self-affection: if the subject attempts to observe its mind, its introspection “changes and displaces” the observed inner object (MAN 4:471). Finally, if the sensory materials of inner sense were the phenomenal experience of synthetical acts, one should be well aware of the sensible qualities of synthetical acts through introspection, since inner sense is continually affected by such acts. Nevertheless, this would not only be incompatible with the proper-material thesis but also with Kant’s own claim that we are “seldom even conscious” of synthetical acts (A78/B103).

5. An Alternative Interpretation of Inner Sense

It is my understanding that both the proponents and opponents of the disparity thesis misunderstand Kant through their interpretation of inner sense. An underlying premise for both sides is as follows: outer sense and feelings provide sensations that are phenomenally conscious; through inner sense, the mind becomes (reflectively) aware of these sensations.[24] More specifically, in the process of self-affection, the subject merely ‘reappropriates’ the conscious sensory materials that are provided by outer sense or feelings;[25] the series of outer sensations or feelings is given additionally a temporal form[26] and perhaps a cognitive[27] or phenomenal[28] ingredient, with nothing more occurring beyond that. In my view, this interpretation is a result stemming from a misunderstanding of the notion of sensory materials of outer experience:[29] it takes these materials as being phenomenally conscious before they enter inner sense. Indeed, we should distinguish between two modes of sensory materials of outer experience: specifically, with or without phenomenal consciousness. The reason underlying this distinction is that, according to Kant, the sensory content of outer sensations can be accessed and processed even if the subject is not phenomenally aware of them. Based on this, my suggestion for solving the disparity problem is therefore the notion that outer sense delivers, in addition to the spatial form, the sensory content of outer experience, whereas inner sense provides, in addition to the temporal form, phenomenal consciousness that pertains to the sensory contents of outer sense. Accordingly, the disparity argument presented at the beginning of this article is unsound as its second premise falsely excludes the possibility that inner sense participates in generating the sensory materials of outer experience. Indeed, phenomenal consciousness of these materials is effectuated by inner sense. Based on these suppositions, the later sections of this paper will examine the related issues.

5.1. Obscure Representations and Inner Sense

A representation is a “determination” of the mind (Br 11:395; Refl 16:76–77); or, plainly stated, a representational “inner state” related to an object (A35/B50; V-Lo/Blomberg 24:40). Such a mental state can represent an object because its properties share a similarity with those of the represented object (LB:30). It is comparable to a picture that “shows the pictorial skill of the soul in its interior” (V-Lo/Blomberg 24:40). One’s being in a representational state does not entail that one is conscious of this state, as attested to by Kant’s division of representations into obscure and clear representations.[30] Representations are obscure if we are not “conscious of having them,” that is, conscious of being in these representational states, when we are in these representational states (Anth 7:135).[31] Representations are clear if we are “conscious of having them” while in these states. Among Kant’s numerous illustrations involving obscure representations, one pertaining to obscure outer intuitions is particularly revealing. This involves a situation in which “I am conscious of seeing a human being far from me in a meadow” without being “conscious of seeing his eyes, nose, mouth, etc.” (Anth 7:135). In this case, the subject “properly infer[s] only that this thing is a human being” (Anth 7:135). The fact that this inference is possible and valid indicates that “one has obscure representations of each of those body parts,” for “the representation of the whole … is composed of these partial ideas” (Anth 7:135). As such, obscure representations of features, such as the eyes, nose, or mouth, contribute to the subject’s recognization of ‘the thing’ in the distance as a human being. Their sensory content is employed in the process of empirical cognition, although the subject is neither consciously aware of having such content (i.e., it lacks state consciousness) nor has a phenomenal consciousness of the individual features.[32]

In view of obscure representations, I will demonstrate in the following four paragraphs that inner sense is responsible for phenomenal consciousness. As, by definition, the consciousness that constitutes the difference between obscure and clear representations is the consciousness of being in inner representational states, that is, in a contemporary turn of phrase, state consciousness (Anth 7:135–136; UD 2:290; Refl 16:80; V-Lo/Pölitz 24:510). This reminds us of inner sense, which provides empirical intuitions of the subject’s inner states. Indeed, compelling evidence demonstrates a close relationship between (state) consciousness in clear representations and empirical inner intuitions. Kant indicates that the former is empirical consciousness (A117n.), thereby implying that it involves sensations. He also mentions that consciousness in a clear representation represents an individual inner state as being present (Anth 7:135; UD 2:290). Therefore, in clear representations, the subject has a sensory consciousness of an individual mental state occurring at a certain point of time. Since it is empirical and temporal in nature, bestowed with a relation to an individual object, state consciousness must involve an inner intuition. That would imply, at least with respect to its sensible component,[33] state consciousness, which distinguishes clear representations from obscure ones, is effectuated by inner sense.

If we consider Kant’s examples of obscure representations more closely (Anth 7:135–136), it is clear that phenomenal consciousness is absent in obscure representations in such a way that the subject cannot notice their content.[34] Even if the subject can merely say something in vague reference to it, such as “it seems that I am aware of something,” according to the definition of obscurity, we nevertheless will not take these representations to be obscure. Therefore, phenomenal consciousness makes a crucial difference between clear and obscure representations. Precisely in this sense, Kant compares state consciousness with light and the absence of state consciousness with darkness (Anth 7:135).

Since it has been demonstrated in the last two paragraphs that both inner sense (more specifically, inner intuitions) and phenomenal consciousness constitute a difference between clear and obscure representations, they must be closely related. Indeed, several other considerations could demonstrate that inner sense brings forth phenomenal consciousness. Phenomenal consciousness is the qualitative aspect of conscious experience (A175/B217). In Kant’s jargon, it is receptively effectuated, for one cannot think a phenomenal experience out. Phenomenal consciousness can thus only be a product of sensibility. As mentioned above (and in Footnote 33), it is inner sense that yields the sensible component of consciousness, which further constitutes a distinction between obscurity and clarity. From these observations, we can infer that inner sense is responsible for producing phenomenal consciousness. Indeed, this relation can be further confirmed by crucial passages in Critique. According to the Anticipations of Perception, the whole range of degree variations of the empirical consciousness of a given phenomenal quality, from zero to any possible degree, falls into the domain of inner sense (A175–176/B217–218). At A177/B220, inner sense is used as a synonym for the faculty of producing “manifold empirical consciousness.” According to its immediate context (A176/B217), the notion of “empirical consciousness” clearly refers to the phenomenal consciousness of sense qualities (A107; Anth 7:161–162).[35] Finally, in §5.2, it will be shown that without apprehension, the subject cannot have phenomenal consciousness of the sensory manifold. As the sensory manifold enters inner sense over the course of apprehension, it can be confirmed once again that inner sense is essentially connected with the phenomenal consciousness of this manifold.

Kant occasionally indicates that consciousness in a low degree is present in some obscure representations (B414n.; Prol 4:307). Could this undermine my argument for the claim that inner sense generates phenomenal consciousness? Indeed, closer consideration reveals the opposite. The weak consciousness, which “suffices [solely] for a distinction” (B415n.), is indeed pure access consciousness without any accompaniment of state or phenomenal consciousness.[36] Even if the weak consciousness were state or phenomenal consciousness, it would not compromise the conclusion that inner sense effectuates phenomenal consciousness, as the argumentation for this does not require the transition from obscure to clear representations to be clear-cut (see also Footnote 52). What it requires is solely that inner sense is conceptually correlated with phenomenal consciousness.

If all these considerations are correct, then how can they further our understanding of the relationship between inner and outer sense? Consider the obscure intuitions of outer objects. They are inner states that, in a sense, depict objects through their properties. Their sensory content can be employed in the cognitive process (through pure access consciousness); therefore, they carry sensory information about the objects, although the subject has neither phenomenal consciousness of these objects nor awareness of these representational states. They are mental “pictures” but are “hung out in a dark chamber” (Refl 16:322). If we take into account that these obscure representations are effectuated by outer sense alone as they have yet to enter inner sense, the first assumption regarding the relationship between outer sense and inner sense can be suggested, namely that outer sense provides sensory content or information about outer objects, and inner sense complements such content with phenomenal consciousness. Thus, pace major interpretative approaches, the interpretation suggested here distinguishes between sensory content and the phenomenal consciousness pertaining to it; additionally, this interpretation traces them back to outer sense and inner sense, respectively. The sensory materials of conscious outer experience thus result from the cooperation of inner and outer sense.[37]

One may object that it is exactly the phenomenal qualities of sensations that bring us new information about the world. Nevertheless, as Kant’s doctrine of obscure representations has indicated, the contribution of informational content by outer sensations to empirical cognition does not necessarily rely on phenomenal consciousness. In contemporary parlance, sensible qualities in virtue of which sensory states differ from one another with respect to their sensory content do not need to occur consciously (Rosenthal 1997: 732–733; 2009: 245–246).[38]

The above assumption seems to rest upon a peripheral phenomenon, specifically upon obscure representations, which are not the concern of the Critique. However, it should be first noted that a substantial portion of our sensible representations that comprise empirical cognitions are obscure: “The field of sensuous intuitions and sensations of which we are not conscious … that is, obscure representations … is immense. Clear representations, on the other hand, contain only infinitely few points of this field which lie open to consciousness; so that as it were only a few places on the vast map of our mind are illuminated” (Anth 7:135, my italics).[39] More significantly, Kant’s account of the generation of empirical cognitions of outer objects can confirm the assumption under consideration. In the following section, I focus on the initial stage of the generation process, particularly in relation to attention, self-affection, and obscurity.

5.2. Apprehension, Attention and Inner Sense

To begin, I will first provide an overview of the proposed interpretation of inner sense. At any given moment during the inspection of our outer world, outer sense provides a mass of sensations (I will call this set of sensations the ‘field of outer sense’). Since the sheer magnitude of these sensations goes beyond the mind’s capacity of awareness, apprehension—which is the synthetical action of taking in and combining sensations into the unity of apperception—is required. Apprehension occurs in the scope of attention; it brings sensory contents provided by outer sense into inner sense and phenomenal consciousness. Sensations that belong to the field of outer sense but lie outside the scope of attention (and therefore apprehension) are obscure.[40] They are in the mind but not yet in inner sense. Therefore, in the course of apprehension’s “running through” of the field of outer sense, the mind takes the obscure products of outer sense into inner sense and accompanies them with phenomenal consciousness. In the subsequent sections, I will argue for this reconstruction from different directions.

5.2.1. The Initial Stage of Empirical Cognition

In a famous passage, Kant elaborates the function of apprehension:

Every intuition contains a manifold in itself, which, however, would not be represented as such if the mind did not distinguish the time in the succession of impressions on one another; for as contained in one moment no representation can ever be anything other than absolute unity. Now in order for unity of intuition to come from this manifold (as, say, in the representation of space), it is necessary first to run through and then to take together this manifoldness, which action I call the synthesis of apprehension, since it is aimed directly at the intuition, which to be sure provides a manifold but can never effect this as such, and indeed as contained in one representation, without the occurrence of such a synthesis. (A99)

This passage describes the function of apprehension by contrasting the epistemic modes of the manifold in an empirical intuition before and after apprehension. In the first mode, the sensory manifold is “contained in one moment,” it cannot be represented “as such”—that is, as a manifold—and remains an “absolute unity”; if it is successively run through and taken together in apprehension, this manifold will be represented as a manifold in a “unity of intuition.”[41] The key to understanding this passage is the concept of absolute unity. Passages containing this notion suggest that “absolute unity” is the opposite of “multiplicity.”[42] This means that it is not possible to discern parts in an absolute unity (Refl 14:59; A340/B398; B419; Refl 17:397). Therefore, in the mode of an “absolute unity,” the manifold of an empirical intuition cannot be represented as a set of manifold sensations. Rather, it remains as an undifferentiated clutter that is in need of apprehension.[43] This reading of the first mode can be reinforced if we consider the meaning of the second mode, which is less obscure. In the “unity of intuition,” the manifold sensations are represented “as such [i.e., as a manifold], and indeed as contained in one representation.” Being represented “as such” means that the subject is aware of the multiplicity of the components of intuitions;[44] being represented “as contained in one representation” implies the same point, since being aware that the manifold belongs to a unity presupposes being aware that there is a manifold.

The initial stage of obtaining empirical cognition thus proves to be an overflow-situation:[45] if all is given in a fleeting moment, the sensory outer manifold exceeds the ‘taking-in’ capacity of apprehension. This overflow-situation results in the subject not being phenomenally aware of the manifoldness. As it cannot experience the manifold “as such” or as a set of various phenomenal qualities, this manifold then remains an “absolute unity” for the subject, devoid of inner multiplicity. This means that it would be phenomenally aware of only a minimal portion of the sensations given by outer sense at one moment.[46] The way to overcome this overflow-situation is to provide apprehension with time: apprehension must “run through” the manifold before taking them together into a unified intuition.[47] In contrast to the initial state of the manifold being “contained in one moment”, the term “run through” refers to the successive exposing of individual sensations to the awareness of the subject. In this process, the elements of the manifold are not only cognitively processed,[48] but also accompanied by phenomenal consciousness. The manifold is thus converted from an “absolute unity” to a phenomenally differentiated unity.

5.2.2. Apprehension, Inner Sense, and Attention

Apprehension is essentially related to inner sense. The synthesis of apprehension is the empirical use of the power of imagination (NKrV 23:18; B527). It operates directly on the sensory manifold and “composes” it into an empirical intuition (B160). It must always stand in “thoroughgoing agreement” with the synthesis of apperception (B162n., 164). Synthesis of apperception, as a purely intellectual combination in unschematized categories, can be applied on a sensory manifold only through the mediation of the transcendental synthesis of imagination with its products, the transcendental schemata (A142/B181; B151–154). Consequently, apprehension—the empirical use of the power of imagination—cannot be separated from the transcendental synthesis of imagination or the transcendental use of the power of imagination. Indeed, Kant even identifies the spontaneity that is embodied by the synthesis of apprehension with the spontaneity that is embodied by the synthesis of apperception (B162n.). Apprehension, as the empirical use of imagination, and the transcendental synthesis of imagination are thus two aspects of one single act.[49] Since it is understanding, in the guise of the transcendental synthesis of imagination, that affects inner sense (B67–68, 153–154), apprehension can be regarded as a process in which the inner sense is affected or, in other words, whereby the sensory manifold is taken into inner sense.[50] This conclusion can be further supported by the fact that apprehension is the process in which the sensory manifold is taken up into empirical consciousness (B160, 202; Anth 7:314n.), which is exactly the sort of consciousness that is provided by inner sense (B160; A176/B217; Br 13:472).

Inner sense is also closely related to attention. In a footnote to §24 of the Transcendental Deduction, Kant states, “I do not see how one can find so many difficulties in the fact that inner sense is affected by ourselves. … In such acts [i.e., attention] the understanding always determines the inner sense” (B156–157n.). It is thus the act of attention where inner sense is affected.[51] The rationale behind this close link is comprehensible. Attention is “the endeavor to become conscious of one’s representations” (Anth 7:131) and the action from which representations are “immediately” made clear (Refl 15:63; V-Anth/Mron 25:1239). Consequently, an obscure representational state becomes a conscious one via attention. As demonstrated above, it is through inner sense that this empirical consciousness of one’s representations is provided (Anth 7:161; Refl 18:611, 613). Therefore, it can be inferred that the scope of attention coincides with the scope of inner sense. Since inner sense, as shown above, is essentially related to apprehension and phenomenal consciousness, a further conclusion can be drawn that the scopes of attention, apprehension, inner sense and phenomenal consciousness coincide (henceforth, ‘the scope coincidence thesis’).[52] In addition, sufficient textual evidence supports the view that the scope of apprehension coincides with that of attention.[53] This reinforces the scope coincidence thesis in another way.

With the scope coincidence thesis, Kant’s account of the initial stage of empirical cognition can be completely reconstructed: assuming a moment at which the subject is faced with a new perceptual scene, outer sense delivers a sensory manifold, that is, a set of sensations that exceeds its capacity of apprehension. The subject’s attention, which is similar to a spotlight, runs through the whole picture, apprehending the details. The sensations that belong to the set of sensations which are initially given but are out of the spotlight of attention form obscure representations that are devoid of phenomenal consciousness. These are real mental items as they can be unconsciously processed. The spotlight of attention brings these obscure sensations successively into inner sense and phenomenal consciousness, as apprehension (or the threefold synthesis) combines them into conscious empirical intuitions of objects. By shifting the attention through the field of outer sense, the subject takes in previously unnoticed details about the outer world while simultaneously becoming aware of the representations that were previously only present in the mind but were yet to be “illuminated” by its consciousness. This account of apprehension implies and hence confirms the assumption stated at the outset of this chapter: outer sense provides obscure sensations that constitute the sensory informational content of an outer intuition whereas inner sense shines the ‘spotlight’ of phenomenal consciousness on them. As such, the issue set forth at the beginning of this article can be answered as follows: the various episodes of our phenomenal experience of the outer world are the sought-after sensory inner manifold.

5.3. Evaluation and Implications

The alternative reading of inner sense can successfully address the difficulties that the disparity theorists have failed to overcome. First, this reading is in line with the afore-cited passages that mentions two types of manifold (see §3). In light of this reading, the cited passage from the Metaphysical Foundations of Nature Science (MAN 4:471) can be paraphrased as follows: the sensory outer manifold can be “held separate and recombined at will” as external objects can be manipulated at will whereas the same cannot be done with the sensory inner manifold, or phenomenal qualities, since inner objects cannot be manipulated at will.[54]

On the alternative reading of inner sense, conscious experience of sensory qualities in outer perceptions is not exclusively effectuated by outer sense but is rather a joint product of outer and inner sense. Nevertheless, this reading can still make sense of Kant’s claim that outer sense provides the proper materials for inner sense. The reason for this is that inner sense merely contributes phenomenal consciousness to outer perceptions whereas all the sensory informational content of outer perceptions, which can be utilized in the obscure mode, is provided by outer sense. This would essentially mean that the ‘what-it-is-like-ness’ is provided by inner sense and thus dependent on specific conditions of the subject. In contrast, the difference between various sensory qualities, which are informational about the objects, can only be traced back to outer sense.

Similarly, the alternative interpretation of inner sense can better serve in explaining the sense in which Kant insists that inner sense has inner states as its objects. As demonstrated above, if not aided by inner sense, empirical intuitions that are merely provided by outer sense would be obscure. Such obscure representational states contain sensory information about outer objects, albeit without the subject being phenomenally conscious of these states and their objects. In apprehension, the subject not only becomes phenomenally aware of the outer objects but also of the obscure representational states, as inner sense is affected in apprehension. In other words, the phenomenal experiences of what it is like to see red, feel warm or taste something sweet—in Kant’s jargon, (clear) sensations (A175/B217; A143/B182–183)—are representational vehicles that, if combined in agreement with forms of intuitions and categories, jointly represent outer objects. When abstracted from their relations to outer objects, to have these clear sensations is simply to experience how (obscure) representational states appear to us as clear sensations are partially generated by inner sense, which effectuates empirical representations of inner states. Thus, one single set of sensations can, if suitably combined, represent both an outer object and an inner state of the mind.[55]

Nevertheless, it should be noted that these inner sensations do not yet constitute a conscious determinate intuition of an inner state on their own. This is because they have not been processed by understanding, since attention and, with it, the synthesis of imagination are directed outward in outer experience. If one directs one’s attention from outer objects to these phenomenal experiences themselves, the latter will be apprehended and composed into a determinate inner intuition of one’s present inner state.[56] This inner intuition, with all its phenomenal qualities, represents the subject as being in a such and such representational state at a given moment; in other words, they represent the subject’s state as appearing as such or such at a given moment. Recall the passage cited in Chapter 3, which states that the subject “cognize[s] [the soul] only as an object of inner sense through the appearances constituting an inner state” (Prol 4:336; see also A107). Thus, inner intuitions represent appearances of inner states. They are genuine representations of the subject in terms of being representations of one’s inner states at different moments rather than representations that merely ‘belong to the subject.’ This explains why Kant repeatedly claims that inner sense provides intuitions of the self. Thus, regardless of where the discussion on whether there is empirical self-cognition in Kant might lead, the broad disparity thesis cannot count on the premise that inner sense does not generate special inner sensations. Since the notion of the appearance of the subject is saved, the transcendental distinction of appearance and things in themselves can be maintained for the case of inner sense.

5.4. Related Issues and Objections

In this section, a number of related issues and objections will be discussed. Through identifying and addressing these possible objections, clarity can be garnered surrounding the more subtle aspects of my account of inner sensations.

5.4.1. Comprehensiveness

I have proposed that inner sense constitutes a difference between clear and obscure representations. Consequently, obscure representations seemingly do not belong to inner sense and hence are non-temporal. This would contradict Kant’s remarks that “our representations … as modifications of the mind … belong to inner sense.” (A98–99, see similarly MS 6:214) and “all of our representations are contained [in] inner sense and its a priori form, time” (A155/B194, see similarly A177/B220). Nevertheless, these passages (henceforth, ‘comprehensiveness thesis’) prove to be innocuous upon closer inspection. The locutions “belong to” and “contained in” are indeed ambiguous. Considering inner sense’s main function of providing inner intuitions, two interpretations are possible: 1) all representations are products of inner sense, that is, they are inner intuitions; and 2) they are, “as modifications of mind”, objects of inner intuitions. As not all representations are inner intuitions, the first interpretation can be excluded. The second interpretation does not refute my interpretation. I have merely suggested that obscure representations are not actually accompanied by inner intuitions. This does not imply that they cannot be objects of inner intuitions and are thus non-temporal. The subject can indeed become sensibly aware of obscure representations by altering perceptual conditions (as in the example of seeing a human being in the distance, Anth 7:135), attention shift (V-Anth/Mron 25:1239), etc.

One may construe “contained [in] inner sense” in a strong manner such that all representations are actually accompanied by inner intuitions. This is, in my view, untenable. Inner intuitions are products of self-affection. Self-affection involves transcendental synthesis of imagination, which is essentially connected with apperception and understanding (A119; B151–152). If the strong reading at issue were correct, then all representations would be essentially connected with apperception and understanding. This leads to implausible consequences: animal minds, in the absence of apperception and understanding, would not be able to have representations (cf. KU 5:464n.; Log 9:64–65); all representations that are merely kept in memory but not actually used would have to be accompanied by inner intuitions (cf. LB:24); and Kant’s position that there are some obscure representations that are totally unaccompanied by consciousness would be unsustainable (B414n.; Log 9:64).

5.4.2. Animal Consciousness

One may object that if only inner sense provides phenomenal consciousness, animals would not have phenomenal consciousness as they do not have inner sense (e.g., Refl 17:469; V-Met-L1/Pölitz 28:276; V-Met-N/Herder 28:938). Such an approach of denying animals phenomenal consciousness would be highly counterintuitive. Nevertheless, we should take the term “inner sense” in Kant’s remarks on animal minds with caution. Such remarks emerge exclusively in his pre-Critical reflections or lecture notes.[57] In these writings, “inner sense” does not refer to the faculty of sensible consciousness of inner states like in the CPR; instead, it refers to the capacity of ascribing disparate mental states to an identical “I” (i.e., pure apperception). Beside textual evidence,[58] several philosophical considerations also support this view. Time, inseparably connected with inner sense as its form, is the “a priori condition of all appearance in general” (A34/B50–51). If Kant deprived animals of inner sense as a sensible capacity, animals would not be able to perceive any temporal appearances. Indeed, humans have an inner sense in the strong sense that their sensible awareness of inner states is inseparably connected with pure apperception and understanding (see Footnote 33). In other words, inner sense in the strong sense provides humans not only with empirical intuitive consciousness of their mental states;[59] in such consciousness, humans are also (either clearly or obscurely) aware of these states as their own.[60] In contrast, animals’ quasi-inner-sense is detached from pure apperception and understanding.[61] By means of quasi-inner-sense, animals can solely be sensibly aware of their inner states without being able to ascribe them to an “I.” Kant’s remarks only deprive animals of the sophisticated cognitive capacity of self-ascription; the sensible nature of inner sense to effectuate sensible awareness of mental states and phenomenal awareness remains preserved.[62]

5.4.3. Indregard’s Account of Inner Sensations

Jonas Jervell Indregard recently proposed that consciousness is a specific kind of inner sensation (2018: 184). This is the most sophisticated alternative to my interpretation thus far. According to him, inner sense has a special ‘phenomenal quality’ which is distinct from phenomenal qualities of outer sensations. He understands this phenomenal quality as “a special quality of ‘presence to mind’” (2018: §9.1). More precisely, inner sensation has the “phenomenal quality of being conscious to a greater or lesser degree” (2018: §5). This account can be illuminated as follows: despite the fact that no alteration in outer sensations takes place (whether alterations in one’s distance to a sound source, the direction of one’s ears, etc.), a sound can maintain the same degree of loudness but vary in its degree of consciousness—depending on the subject’s focus of attention, level of concentration, tiredness, concurrent sensations, etc. (see Indregard 2018:§§5–7, 9.1 and 9.4).[63] Consider what you will be aware of when heavy construction work is being conducted outside and you gradually become immersed in philosophizing (2018: 188; I have slightly modified his example). The outer sensation remains strong, whereas the extent to which you are aware of it gradually diminishes and “plausibly, the phenomenological character of your perception changes” (2018: 187). Such alterations of phenomenal characters that occur independent from alterations of outer sensations manifest the phenomenal contribution of inner sensations, which is precisely the long-searched-for sensory inner manifold.

Indregard maintains that a conscious perceptual state involves phenomenal qualities of outer sensations and, additionally, the specific phenomenal quality of inner sensations. However, what does it mean that the devoted thinker has “strong outer sensations but weak inner sensations” (2018: 188)? Indregard seems to propose that the subject’s phenomenal awareness of the loudness’ “presence” is weak. The thinker experiences the high volume; nevertheless, the phenomenal experience of this loudness, as a real mental occurrence, is less ‘present’ to the mind and the thinker also experiences this presence phenomenally. The subject must thus simultaneously experience the high loudness and its low ‘presence,’ both in the phenomenal sense. How can this be imagined? I would contend that this requires a highly sophisticated notion of phenomenal consciousness, one that would impose a heavy proof burden on Kant. At any rate, Indregard’s account of the devoted-thinker-example relies on an implicit premise that loudness, as a phenomenal quality, depends solely on outer conditions of perception (one’s distance to the sound source, the direction of one’s ears, etc.). As long as outer conditions remain constant, the loudness remains the same strength. Thus, we need another factor to account for the alteration of the phenomenal character that the thinker experiences. That premise, however, seems unfounded: Why is it not possible to say that, for the thinker, the noise appears ‘quieter’ as it approaches the periphery of attention? The alteration of phenomenal character in the absence of outer alteration can be explained by alteration of phenomenal qualities themselves rather than by postulating an additional special quality of ‘presence to mind’ (cf. Indregard 2018: 188 fn. 44).

Finally, further textual evidence is needed for the purported specific phenomenal quality of inner sensation (Indregard 2018: §9.1). Among the three passages that Indregard advances as evidence, one particular passage holds the most promise, which is as follows: “Consciousness is a quality of thinking and thus has a degree, for every quality always has a degree” (V-Met-L2/Pölitz 28:590). While having potential, the passage is nevertheless ambiguous. For instance, the notion of “quality of thinking” could refer to a kind of cognitive phenomenology, that is, what it is like to have spontaneous cognitive acts. Phenomenal qualities of thinking, however, are still distinct from the “special quality of ‘presence to mind’.”[64] The notion at issue does not even have to be concerned with phenomenal qualities as it can arguably also refer to the extent of the subject’s cognitive access to its thoughts (see Liang 2017a; 2017b). Indeed, as Kant speaks of the degree of empirical consciousness (A176/B217), he is referring to nothing other than the degree of the phenomenal qualities of outer experiences.

5.4.4. Objection from Transparency

The alternative interpretation apparently falls prey to accusations from the transparency thesis. Transparency theorists hold that we are unable to perceive the intrinsic features of a sensation through introspection; all we can perceive in such introspection are the features of the objects of sensations.[65] We usually “see right through” perceptual states to external objects and cannot perceive the perceptual states themselves. In other words, inward attention does not reveal any feature of experience that is not traceable merely to the appearance of outer objects (see Harman 1990; Speaks 2009; Tye 1992). When applying this thesis to Kant’s doctrine of inner sense, one could argue that as there are no sensibly detectable features of inner states, the subject cannot perceive these states (Schmitz 2015: 1049). Consequently, there are no such things as empirical inner intuitions (Schmitz 2015: 1048).

In defense of the alternative interpretation, it first has to be noted that the transparency thesis is still far from reaching shared consensus, and it faces many counterexamples that need to be overcome (see Martin 2002; Smith 2008; Stoljar 2004). Thus, it does not constitute a knock-down argument against an interpretative resolution. Even if the transparency thesis were true, it would not undermine the alternative interpretation. Kant does not, in any degree, claim that one perceives one’s mental states because one perceives certain types of intrinsic mental features. He simply takes it for granted that the subject’s awareness of one’s inner states is an empirical inner intuition (B157n., BXLI n.), that is, a perception. It is nevertheless possible to defend his stance without relying on the controversial notion of perceiving intrinsic mental features.

Firstly, a mental state is an individual mental occurrence in time. One’s awareness of being in a mental state must involve an intuition of this state, since a concept, as “a representation of what is common to several objects” (Log 9:91), can be related to an individual object only by being first related to an intuition (A19/B33). As an intuition of a mental state in time is not a pure intuition of a temporal position or duration, the intuition must be empirical—that is, the awareness of inner states must be perceptual.

Secondly, as demonstrated above, a representation is an ‘obscure’ or phenomenally unconscious state if it does not enter inner sense. When the subject attends to an outer object, inner sense furnishes the representation of this object—this is provided merely by outer sense—with phenomenal consciousness. When the subject has a conscious outer experience, it de facto also has inner awareness of its states (“of” in a de re sense), which is generated by inner sense: To have phenomenal consciousness of sensory qualities of outer objects is also to experience what it is like to be in the inner states that represent these outer objects. To experience what it is like to be in some inner states is, in Kant’s jargon, to have an (indeterminate) inner intuition of these states. Consequently, no extra act of introspection of intrinsic mental features is required to acquire intuitions of mental states. Nevertheless, one may still object that we normally do not realize that we are experiencing inner states when we are experiencing outer objects. In favor of the alternative interpretation of inner sense, it could be countered that in conscious outer experiences, we merely have obscure inner intuitions, since all our attention, which can make an intuition clear, is directed outward. Conscious (or clear) inner intuitions can be obtained by reinterpretation through thoughts: we attend to the qualities of outer objects, abstract them from their relation to these objects, and reinterpret them as feelings of what it is like to have the current mental state.[66] As this mental state is, in this course of events, conceptually determined and consciously ascribed to the subject, the subject obtains a conscious determinate intuition of its inner state.[67] In other words, an act of reinterpretation rather than a sensible introspection of mental features is required in order to obtain conscious intuitions of mental states.

6. Conclusion

In this paper, I have examined an influential interpretation of Kant’s notion of inner sensation—the narrow disparity thesis. I argued that this reading not only contradicts textual evidence but also vitiates Kant’s doctrine of empirical self-cognition. My analysis has shown that major defenses of both the disparity and the parity thesis fail due to a shared view of the relationship between inner and outer sense. Drawing on Kant’s account of obscure representations, I suggested that inner sense endows obscure outer intuitions with phenomenal consciousness. To extend this insight to more general cases of perceptual awareness, I reconstructed the initial stage of apprehension and developed an alternative interpretation of inner sense: outer sense provides the mind with empirical contents that are not intrinsically conscious representations; over the process of apprehension, inner sense accompanies such contents with phenomenal consciousness. Therefore, sensory qualities which are consciously experienced are joint products of outer and inner sense. These phenomenal qualities can be regarded as the long-searched-for sensory inner manifold, not only as they are products of inner sense but also because they are representational vehicles for the sensory representation of an inner state. In conclusion, with regard to the material aspect at least, inner sense stands on par with outer sense.


Many have given me helpful comments and feedback on earlier versions of this paper; I am especially grateful to Wei Cheng and two anonymous referees. I am also grateful to Xingming Hu, Hong Li, and audiences at Beijing Normal University. This work was supported by the Fundamental Research Funds for the Central Universities of China and by China Postdoctoral Science Foundation.


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Anthropologie in pragmatischer Hinsicht
Die falsche Spitzfindigkeit der vier syllogistischen Figuren erwiesen (AA 02)
Erste Einleitung in die ‚Kritik der Urteilskraft‘
Preisschrift über die Fortschritte der Metaphysik
VKritik der reinen Vernunft
Kritik der Urteilskraft
Logik Bauch
Logik Jäsche
Metaphysische Anfangsgründe der Naturwissenschaft
Die Metaphysik der Sitten (AA 06)
Nachträge zur Kritik der reinen Vernunft
Opus Postumum
Prolegomena zu einer jeden künftigen Metaphysik, die als Wissenschaft wird auftreten können
Recension von Schulz's Versuch einer Anleitung zur Sittenlehre für alle Menschen (AA 08)
Untersuchung über die Deutlichkeit der Grundsätze der natürlichen Theologie und der Moral
Vorarbeit zur Kritik der praktischen Vernunft
Anthropologie Mrongovius
Logik Blomberg
Logik Philippi
Logik Pölitz
V-Met-K 3E/Arnoldt
Ergänzung Metaphysik K3
Metaphysik L1
Metaphysik L2
Metaphysik Mrongovius
Nachträge Metaphysik Herder
Metaphysik von Schön, Ontologie


    1. Experience (“Erfahrung”) in Kant’s sense requires more than sensations and intuitions as it results from the subject’s reflection on empirical intuitions that brings these intuitions under concepts of understanding (Anth 7:142). I employ the term ‘experience’ generally in Kant’s sense. However, in ‘conscious experience’ or ‘phenomenal experience,’ it is used in the English sense, viz., a mental state with a particular phenomenology.return to text

    2. For details about the broad theses, see Kraus (2019).return to text

    3. Quotations from Kant’s works are from the Akademie-Ausgabe and Immanuel Kant: Logik-Vorlesungen (Felix Meiner Verlag, 1997). The Critique is cited by the standard A/B edition pagination and the other works by volume and page. Translations are based on the Cambridge Editions of the Works of Immanuel Kant (eds. Paul Guyer and Allen Wood). I regularly consulted translations from the Hackett editions (ed. Werner Pluhar). Specific texts are abbreviated, as indicated at the end of this paper.return to text

    4. If not otherwise indicated, all occurrences of the term ‘intuition’ refer, for the sake of simplicity, to empirical intuition.return to text

    5. All types of mental states can be the object of inner intuitions (A357–359; A443/B471). Kant specifies the notion of the object of inner intuitions roughly in three ways (for a slightly different classification, see Mohr 1991: 67ff.): it is 1) “the self” (B68), “the soul” (A342/B400; B415; A683/B711; A385), “the (thinking) I” (A342/B400; A361, 379) or the “thinking being” (A380); 2) “the self” (or “the I”) and its states (A38/B55; A22–23/B37; A33/B49; B471; A368, 371; Refl 15:66); 3) inner states (A22–23/B37; A98–99, 107; A371). Indeed, according to the Paralogisms chapter (A350, see also A22–23/B37), the object of inner intuitions or inner sense can neither be the soul, the thinking being, nor the self (which Kant generally treats as equivalents). Rather, the soul, or the self, is the transcendental object of inner sense (A360–361; Refl 18:31). It is inner states that are the object of inner intuition or inner sense (A107, 371; Prol 4:336; see Rosefeldt 2006: 290; Wolff 2006: 267; Kraus 2019).return to text

    6. See Paton (1936b: 388–389), Collins (1999: §11), Gardner (1999: 299–300), Allison (2004: 279, 283), Wolff (1963: 193ff.), Valaris (2008), Schmitz (2015: 1045).return to text

    7. See, e.g., Paton (1936b: 238–240), Allison (2004: 283), Kemp Smith (1923: 292ff.), Collins (1999: 207), Emundts (2013: 68ff.), Schmitz (2015), Brook (1994: 77), Valaris (2008: 2), Dyck (2006: 39–40).return to text

    8. See also BXXXIX n. and the loose leaf On Inner Sense (ll. 9–11). Proponents of this view are, e.g., Allison (2004: 277), Paton (1936b: 389).return to text

    9. Refl 17:366; A357–358; V-Met-L1/Pölitz 28:279. See Emundts (2007), Kraus (2013).return to text

    10. KU 5:206. As Kemp Smith states, the proper-material claim speaks “from the limited point of view of a critique of knowledge” (1923: 293–294). See similarly Paton (1936a: 99; 1936b: 397), Krüger (1950: 187), Collins (1999: 109, 113–114), Valaris (2008), Kraus (2013: 335–337). Conscious thoughts are, as mental states, also objects of inner sense. It is nevertheless uncertain whether Kant thinks that there are any specific phenomenal experiences that are linked to conscious thought. As far as I am aware, he gives only one vague hint regarding this at V-Met-L2/Pölitz, 28:590. While I have the tendency to give a positive answer on this point (see similarly Indregard 2018), I am not going to provide one, as it goes beyond the scope of this paper.return to text

    11. E.g., Krüger (1950: 187) construes inner manifold as pleasure and displeasure. Cf. Mohr (1991: 100).return to text

    12. Against the conventional interpretation (Paton 1936b: 389; Mohr 1991: 168–171), Nakano (2011) argues that self-affection and outer affection are of a singular process. If this were true, the production of outer sensations would always involve transcendental synthesis that effectuates self-affection. There would be, contrary to Kant, no “manifold that is antecedently [i.e., prior to self-affection] given in the subject” (B68) and hence no intuition that “precede[s] any act of thinking something” (B67). For more counter-evidence, see V-Met-K 3E/Arnoldt 29:982.return to text

    13. See Allison (2004: 278), Valaris (2008: 2–3). Cf. Kraus (2013), Krüger (1950).return to text

    14. There are other candidates for inner manifold from contemporary discussions that were presumably unknown to Kant. See Lycan (2004), O’Conaill (2019).return to text

    15. A few commentators hold that the self is an empirical substance for Kant (e.g., Chignell 2017). For a review of the controversy and a rejection of this view, see Kraus (2019).return to text

    16. See Allison (2004: 279), Emundts (2007: 197–199). Collins maintains that inner sense is not “a further source of inputs for knowledge of reality” (1999: 109, 115).return to text

    17. Allison (2004: 280), Caranti (2007: 134). See similarly Paton (1936b: 422), Brook (1994: 94).return to text

    18. Refl 18:680; see similarly Kraus (2019). Valaris (2008: 3) offers another objection to Allison. One may raise the concern that we cannot distinguish the self from its states without regarding the self as persisting through the changes in its states. For that distinction, one does not have to cognize the self as a substance; rather, merely thinking of the self “as if” it were a substance is sufficient (A672/B700; A350, 400; MFNS, 4:542). I thank an anonymous referee for this point.return to text

    19. Especially in two newly added parts of the B-edition on self-cognition (B68–69, 156). Kant explicitly maintains that the subject is represented as appearances in inner sense at B68. See also A34, 107, 379–380; A491/B519; Refl 18:680; Anth 7:142–143. He mentions inner appearances at A478/B506n., A492/B520, A551/B579, A673/B701, A690/B718.return to text

    20. See Kemp Smith (1923: 294), Paton (1936b: 389), Collins (1999: 114), Allison (2004: 277).return to text

    21. The question as to why Kant gives such misleading remarks goes beyond the scope of this paper. For more on this point, see, e.g., Collins (1999: 111–113).return to text

    22. Gardner (1999: 300) convincingly refutes another defense of this approach based on A32–36/B49–53.return to text

    23. Mohr (1991: 167ff.). See similarly Dyck (2006: 41–42).return to text

    24. See, e.g., Kemp Smith (1923: 294), Wolff (1963: 199), Collins (1999: 109, 113), Allison (2004: 278–279), Melnick (2008: 112–113), Caimi (2002: 101–102). One exception is Indregard (2018: 188). See §5.4.3 of this article.return to text

    25. Allison (2004: 278–279). See also Paton (1936b: 392, 397), Wolff (1963: 197, 199), Collins (1999: 113), Melnick (2008: 112–113). For a systematic review of the reflection theory of inner sense, see Ameriks (2000: 243ff.).return to text

    26. “To outer sense is due both their [sc. representations of outer objects] content and their spatial form; to inner sense they owe only the additional form of time; their content remains unaffected in the process of being taken over by a second sense” (Kemp Smith 1923: 294, my italics).return to text

    27. See the afore-cited passages from Schmitz (2015), Krüger (1950: 186).return to text

    28. See, e.g. Mohr (1991: 167ff.) or Melnick (2008: 112–113).return to text

    29. For the sake of simplicity, I will henceforth stay in the context of Critique and leave feelings of pleasure and displeasure out (see §2). However, the conclusion that I will draw can be extended to these cases with minor modifications (see Footnote 55).return to text

    30. Compelling evidence for the view that representations are not intrinsically conscious can be found at B414n., A320/B376–377, Log 9:64, V-Lo/Blomberg 24:132, LB:24.return to text

    31. We could be aware of obscure representations only indirectly, e.g., by means of inference (Anth 7:135; V-Met/Mron 29:879; V-Met-L1/Pölitz 28:227), attention shifts (V-Anth/Mron 25:1239) or altering the perceptual conditions (Anth 7:135).return to text

    32. The cognitive access of the mind to such sensory content is, in contemporary parlance, access consciousness (Block 1995). For access consciousness in Kant, see Emundts (2013: 62), Liang (2017a; 2017b), and Longuenesse (2019).return to text

    33. In V-Lo/Philippi 24:410, Kant explicitly connects state consciousness in clear representations with inner sense. Recently, Indregard (2018) argues that for Kant, state consciousness is inner sensation. See also Schulting (2015: 97). Indeed, state consciousness is a joint product of inner sense and pure apperception (Anth 7:141; OP 22:31; V-Met-L2/Pöblitz 28:84. See Liang 2017a; 2017b), since in being conscious that one is representing something, one already ascribes this representational state to herself. This act of self-ascription is performed by pure apperception (B132; A117n.). In other words, state consciousness consists of pure apperception and empirical apperception (Anth 7:141–142). Pure apperception is related to understanding (B134n.; A119) and hence involves spontaneous acts (self-ascription, synthesis according to categories, etc.); empirical apperception that is generated by inner sense features inner sensations and phenomenal consciousness (Anth 7:141, for a detailed account, see Liang 2017a; 2017b). Henceforth, I will leave out this complication since what concerns us is the sensible part of state consciousness that inner sense is responsible for.return to text

    34. In another illustration, Kant says that although one cannot discern individual stars in the Milky Way, he has obscure representations of each one, because every light ray affects the retina (Anth 7:135). Clearly, one cannot be phenomenally aware of individual stars.return to text

    35. Hanna holds a similar view in (2005: 261) and (2008: 58).return to text

    36. See Footnote 32. In Kant, consciousness could be the full-blown apperceptive consciousness (see Footnote 33) or the weak version in obscure representations that is pure access consciousness. Owing to the limited scope, I cannot provide a detailed account here. For more thorough treatments of this issue, see Liang (2017a; 2017b), cf. Longuenesse (2019); for a similar distinction of two kinds of consciousness, see Grüne (2009: 74f.), Schulting (2012).return to text

    37. Kraus and Indregard are the only interpreters I know who broach the issue that inner and outer sense must be cooperating in every act of outer sensation. Nevertheless, they have a different reading concerning this cooperation and the exact contribution of inner sense than the reading suggested here (Kraus 2013: 342; Indregard 2018: §§5, 6, 7, 9.1).return to text

    38. I nevertheless do not claim Kant to be a higher-order theorist like Rosenthal due to the subtleties of their doctrines that go beyond the scope of this paper.return to text

    39. Kant is quite clear at V-Met-L1/Pölitz 28:228 and V-Lo/Philippi 24:409 that these obscure representations occupying an immense field in mind are cognitions.return to text

    40. Kant allows for unconscious or obscure sensations (e.g., Anth 7:135; RezSchulz 8:11). Henceforth, “sensation” refers to clear/conscious sensation if not otherwise noted.return to text

    41. Although Kant speaks of the first mode in a subjunctive mood, this does not mean that it is not real. The “running through” of apprehension conceptually presupposes mental states in the first mode. This mode is indeed the so-called “synopsis” of intuition (A97; see Paton 1936a: 354; Waxman 1991: 218–225; Longuenesse 1998: 37; Allison 2015: 207). Sensations out of attention are in the first mode—they are “contained in one moment” and cannot be apprehended at once (we will return to this point below). The reason why Kant uses a subjunctive mood might be that episodes of empirical awareness that are totally in the first mode are seldom as a portion of sensory manifold (that is, as we will see later, the sensory manifold in the scope of attention) is always already processed by apprehension.return to text

    42. “Substance is either absolute unity, or in itself multiplicity: compositum substantiale” (Refl 17:739). See also A340/B398, B419.return to text

    43. The majority of commentators hold a similar view concerning this passage despite minor differences. See, e.g., Longuenesse (1998: 38 n.10, 271–272), Thöle (1991: 216–217), Guyer (1987: 148), Wolff (1963: 152–153), Mohr (1991: 175ff.), Grüne (2009: 154). Cf. Henrich (1976: 21). For critical views against Henrich, see Wolff (1963: 152–153), Grüne (2009: 153–154), Allison (2015: 210).return to text

    44. At this stage, it is enough that the subject is aware that there are different items. There is no need to distinguish all components of the manifold from one another or be aware of individual components, as that would produce a so-called “distinct intuition” (Anth 7:138), which is unnecessarily strong for apprehension. See Grüne (2009: 158ff.).return to text

    45. See similarly Wolff (1963: 153), Guyer (1987: 148), Hoppe (1983: 180), Carl (1992: 153), Longuenesse (1998: 37–38), Grüne (2009: 154), Kitcher (2014: 34).return to text

    46. This portion of sensations falls into the scope of attention, of which the subject can be immediately aware within a fleeting moment.return to text

    47. For similar interpretations on apprehension being related with the effectuation of phenomenal awareness of the sensory manifold, see Waxman (1991: 202), Grüne (2009: 184).return to text

    48. The cognitive contribution of apprehension and its relation to reproduction and recognition, like many other aspects of apprehension, are controversial topics of prolonged discussions (for an overview, see Grüne 2009: 150ff.). The so-called standard interpretation (see Waxman 1991: 193) regards apprehension, reproduction and recognition as inseparably bound together so there is only one single threefold synthesis (A97) rather than three different ones. Major proponents of standard interpretation include Paton (1936a: 354, 361–362), Wolff (1963: 149ff.), Prauss (1971: 278), Hoppe (1997: 167), Guyer (1987: 106), Carl (1992: 147), Longuenesse (1998: 35–36), Grüne (2009: 149, 183ff.), and Allison (2015: 205). According to this reading, apprehension is the initial step of a single synthesis that combines sense impressions into an empirical intuition. In contrast, Waxman (1991: 185–186, 196, 202) is of the opinion that apprehension is in itself an independent sensible process; it merely presents sensible manifold to spontaneous capacities without any cognitive contribution. See similarly Zöller (1984: 123), Olk (2015: 99). In this paper, I adopt a position that is compatible with both parties, namely that the three syntheses are one single act as far as empirical cognition is concerned (Waxman 1991: 199ff.; Longuenesse 1998: 35). I remain neutral about other controversial issues around apprehension so far as they are irrelevant for my argumentation.return to text

    49. See also a passage in Nachträge zur Kritik der reinen Vernunft (23:18–19).return to text

    50. Allison (2004: 282) offers another route to this conclusion.return to text

    51. See also Refl 18:680, FM 20:270. Some commentators argue that the transcendental synthesis of imagination that affects inner sense is executed in or even identical with attention. See Dyck (2006: 41), Merritt and Valaris (2017).return to text

    52. Consciousness, inner sense, and all other faculties have a “degree, which can always be diminished” (B414–415). Therefore, the identical scopes of attention, inner sense, and phenomenal consciousness do not have clear-cut boundaries. Nevertheless, the degrees of the three covary as they are, as already demonstrated, essentially related to each other. For the sake of simplicity, I will neglect this complication as it does not influence the matter at hand.return to text

    53. Kant translates “Auffassungsvermögen” with “attentio” in Anth 7:138, and “Auffassung” with “apprehensio” (KU 5:189, 192, 251; Anth 7:142; Br 11:515; EEKU 20:220). See similarly Merritt and Valaris (2017: 572, 582, 584).return to text

    54. For a critique of this passage, see Hatfield (1992: 222).return to text

    55. When stated precisely, an inner state at one moment is a sum of various sensations, such as sensations arising from outer objects, bodily sensations, and sensations pertaining to pleasure and displeasure. Pleasure and displeasure do not have the two-faced values such as outer sensations as they are “subjective sensations” that do not have any representational content (KU 5:206–207). However, the alternative interpretation of inner sense still applies to pleasure and displeasure. First, although feelings of pleasure and displeasure cannot form an intuition related to an object, they are still inner states and thus objects of inner intuitions. Secondly, Kant extends the doctrine of obscure representation to pleasure and displeasure (e.g., Refl 15:65–66, 665). Therefore, analogous to the case of outer sense, the distinct sensory content of pleasure and displeasure is generated by the faculty of pleasure and displeasure whereas their phenomenal experience is effectuated by inner sense. Textual evidence for inner sense’s effectuation of phenomenal consciousness pertaining to the subjective sensations can be found at KpV 5:23.return to text

    56. Attention contains synthetical acts according to concepts of understanding (B156–157n.). Therefore, if directed inward, attention provides determinate inner intuitions from previous indeterminate inner intuitions. The indeterminate inner intuitions of inner states are obscure if the subject’s attention is directed outward since, as mentioned, attention is the act by which a representation is made clear. For Kant’s account of indeterminate inner intuitions, see Refl 18:680.return to text

    57. Refl 17:469 was written between 1769 and 1770, V-Met-L1/Pölitz 28:276 in mid 1770s and V-Met-N/Herder 28:938 between 1762 and 1764.return to text

    58. V-Met-L1/Pölitz 28:276; DfS 2:60. See similarly McLear (2011: 9–10) and extensively Ameriks (2000: Ch. 7); cf. Fisher (2017).return to text

    59. I.e., they are conscious of these mental states as objects. See similarly Kraus (2019).return to text

    60. Pure apperception “accompanies … all representations at every time in my consciousness” (A362–363).return to text

    61. One may further object that human’s inner sense is activated by the understanding’s spontaneous acts while there are no comparable acts that could affect the quasi-inner-sense in animals. Indeed, animals are capable of imagination (V-Met-L1/Pölitz 28:277; V-Met-L2/Pölitz 28:594; V-Met/Dohna 28:689–690), association (Br 11:52), reproduction (V-Met/Mron 29:884), and reflection (KU 20:211). Although these are, in contrast with their analogues in human, not genuine spontaneous acts, it is arguable that these ‘quasi-acts’ affect animals’ quasi-inner-sense.return to text

    62. See similarly McLear (2011). For more on animal consciousness, see Fisher (2017) and Indregard (2018: §9.3).return to text

    63. I thank an anonymous referee for clarification.return to text

    64. That consciousness involves a cognitive phenomenology can be accommodated by my interpretation after slight modifications. I will not pursue this textual clue owing to the lack of further textual evidence.return to text

    65. “Look at a tree and try to turn your attention to intrinsic features of your visual experience. I predict you will find that the only features there to turn your attention to will be features of the presented tree, including relational features of the tree ‘from here’” (Harman 1990: 39; see also classically Moore 1903: 450).return to text

    66. See similarly Krüger (1950: 186).return to text

    67. Thus, the generation of conscious determinate inner intuitions also requires operations of understanding, just as conscious determinate outer intuitions are joint products of sensibility and understanding.return to text