At the beginning of the second edition of the Transcendental Deduction, Kant begins §15 by asserting that any manner of combination or synthesis of representations is an action of the spontaneity of the understanding as opposed to being previously combined before having received it in sensibility and sensible intuition, asserting this because he wants to point out that the manifold given in intuition is not synthesized as a manifold through intuition, but through the understanding, since any synthesis is a representation of the synthetic unity of the manifold. This mirrors previously where Kant established intuition as a receptive faculty, merely intuiting and receiving external data through sensibility through the forms of space and time, and the understanding as active in taking that data and organizing it through the categories extracted from the table of judgments. This point is further illustrated when he notes that we represent nothing combined in an object without previously combining it ourselves, therefore, synthesis must precede any form of analysis. With this, we can begin to see Kant leaning in the direction of establishing his categories as necessary for any experience through appearances to occur. Particularly, with how the categories and intuitions combine.

§16 establishes the notion of apperception and its relation to the manifold given in intuition. Kant shows with the “I think” or apperception that for any representation to be mine, I must be able to ascribe it to my self-consciousness. This doesn’t necessitate that I must consciously think and actively self-ascribe every representation for them to be mine, but necessitates that it must be possible for them to be taken up by my self-consciousness for them to be my representations. This representation of the apperception as a persisting self-consciousness throughout all my representations belongs to the understanding and is thus called the pure or original apperception as opposed to an empirical apperception. The empirical apperception is the inner sense, which is the mind intuiting itself and its various states throughout time, which disperses itself and does not relate to the persisting subject. The pure apperception, however, does not come from the analysis of the presence of consciousness in each representation, but being conscious of the synthesis occurring when adding one representation to another. We find our self-consciousness in the relations we establish between representations, not merely the representations themselves. Again, Kant reaffirms that synthesis must precede any analysis, when he infers that the synthetic unity of apperception must precede the analytic unity of apperception, i.e., the ability to synthesize a manifold of representations in one consciousness makes it possible for me to represent the identity of consciousness in those given representations. Kant also shows that the apperception absent of a synthesis of a given manifold through intuition would be nothing since neither the “I” nor the understanding supply the manifold of representations, thus reaffirming that the understanding synthesizes the given manifold from sense intuition, and one can apperceive the persisting consciousness through that synthetic unity.

§17 begins with restating the results of the Transcendental Aesthetic, that space and time as forms of intuition and intuitions themselves must be the condition that all the manifold given through sensibility must stand under. Kant relates that relation of intuition to sensibility to the relation of intuition to the understanding, saying that the original synthetic unity of apperception is the ultimate condition that all intuition must stand under, i.e., all my intuitions must stand under a singular self-consciousness synthetically. It is at this point that he introduces the concept of objects. It would seem at this point that he would be directly responding to David Hume’s theory that objects are merely bundles of properties with no inherent, deeper unity. For Kant, however, objects are concepts in which the manifold of a given intuition is synthetically unified. Now, because self-consciousness is the consciousness of the synthetic unity of consciousness, any synthetic activity under that consciousness is grounded by the synthetically unified self-consciousness. And cognitions are those determinative relations between given representations and concepts. So, the first pure cognition of the understanding is the original synthetic unity of apperception. Thus, space as a form of outer sensible intuition isn’t cognition but gives the manifold of intuition form for possible cognition. To cognize something for Kant is to perform synthesis of a manifold, unifying consciousness and then unifying the manifold in the concept of an object. Therefore, the synthetic unity of consciousness becomes the objective condition for all cognitions, that which all intuitions must stand under to become an object for that consciousness. This principle only holds up for that apperception that the manifold of intuition isn’t given through understanding, for if the manifold already existed in the understanding, then it wouldn’t have to be taken up and synthetically unified within it.

The transcendental unity of apperception is thus the objective unity since it is that which unifies the manifold of intuition into the concept of the object. Being conscious of inner sense through associations of representations is a subjective unity of consciousness. It is subjective because intuition is received empirically, as objects of the intuition of inner sense, rather than through the external senses. The subjective unity of consciousness is only an appearance of unity via association and is, therefore, contingent on the empirical circumstances of each person and only subjectively valid, rather than being universal and necessary. This is to say that the extent to which I can be conscious of myself and my manifold of internal intuitions as a succession of states depends on my empirical conditions and is different than my being conscious of myself through my syntheses of intuitions of a given manifold through my sense capacities. And since time as an intuition must stand under the original synthetic unity of consciousness, because of the relation between the manifold of intuition and apperception, the empirical unity of apperception is grounded by the original synthetic unity of apperception.

Kant now wants to connect judgments to the objective unity of apperception. Judgments, for Kant, are objectively unifying through the copula. When a judgment is objectively valid, copulas establish a necessary relation between the subject and the predicate. This provides necessary relations as the object is determined for the necessary unity of self-consciousness. For example, because the manifold of intuitions is united in my self-consciousness, I can make a judgment claiming, “The bag is red”. In that judgment, I am establishing a necessary relation between my representation of the bag and my representation of redness and combining them into an object for me, because my consciousness is unified. In short, judgments are combining the manifold of intuition into the objective unity of self-consciousness. And because the categories are “functions for judging”, the manifold of intuition must stand under the categories.

At this point, Kant has established the synthetic unity of apperception as the supreme unity that all my representations must stand under, their objective validity, and their connection to the categories in synthesizing by asserting objectively valid judgments. One might think that Kant’s work here is finished. However, by observing the discourse among Kantian scholarship, the second half of the B Deduction is one of much contention. This half of the Deduction is described as “labyrinthine” by some in Kantian scholarship, especially for the relatively uninitiated into Kantian thought. Therefore, I will be relying upon the interpretations of various Kantian scholars to attempt an interpretation for myself. First, I will single out two of Dr. James Conant’s possible readings of Kant: a restrictive and nonrestrictive reading. According to
Conant, a restrictive reading of Kant would entail viewing the subjective conditions for experience as restrictive to the nature of objects to which assert as objectively valid, as well as diluting their objective validity (as they are “for us”). Further, this restrictive reading would lead to viewing the categories as imposing forms of unity on objects given in sense intuition. A nonrestrictive reading of Kant would view subjective conditions not just as conditions of subjectivity, but as conditions under which the possibility of comprehendible objectivity lies. This nonrestrictive reading would imply that the understanding and sense intuition are more intertwined and less hierarchical than previously depicted, and this reading would later entail that the categories do not merely subsume what is given through sensibility, but that the categories are already involved in what sensibility gives.

To establish a non-restrictive view of the categories, Kant must make the case that what is given in sense intuition isn’t merely being acted upon by the understanding. He must establish sense intuition as an equal partner in fostering objective validity. He begins his case in §22 when he distinguishes between what it means to think of an object versus cognizing one. Cognizing an object is having both the concept as well as empirical intuition. Thinking is akin to representing an object when its presence is absent in empirical intuition. This is what Kant later calls the imagination, where the object remains a mere thought rather than something actual. He goes on to say in §23 that the categories can extend beyond the limits set in the Transcendental Aesthetic, beyond the forms of space and time or objects of sense intuition, to what he calls objects of intuition in general. Yet the categories operate with sensible intuitions in order to be objectively valid. Therefore, without sensible intuitions as content, they would again be empty concepts. So,
the categories are merely the conditions of the possibility of experience through empirical cognition. Therefore, Kant establishes sensible intuition as necessary as without it, the categories wouldn’t have objective validity.

Yet, the manifold given empirically doesn’t entirely depend on the conditions of the subject. Dr. Mario Caimi introduces the next problem for Kant in showing that the categories depend on the manifold of empirical intuition if they are not to be empty. He describes that since the manifold that is given in intuition is independent in itself, the application of the categories and their synthesis becomes difficult here since the nature of the manifold is “utterly alien to the
subject”. Thus, the work going forward lies in reconciling the “alien nature of the manifold” with the unity that the apperception and its categories ascribe and proving the categories aren’t merely empty without content.

At this stage of the deduction in §24, the pure concepts of the understanding are again concerned with objects of intuitions in general, which includes sensible objects, but on this conception of the pure concepts, they are “mere forms of thought”, yet to cognize any determinate objects. These forms only concern objects given as appearances. When we abstract the pure concepts of the understanding from the manifold of sensible intuition and toward the manifold of intuition in general, that is what Kant calls intellectual synthesis. The synthesizing of the manifold of sensible intuition is called figurative synthesis. They are both transcendental since they both are concerned with being conditions for possible cognition. And if figurative synthesis is thought of as belonging to the synthetic unity of apperception, it is called the transcendental synthesis of the imagination. Once again, imagination is the ability to represent an object even when it isn’t present in intuition. And if all our intuitions are sensible, the imagination belongs to sensibility since it is subject to the conditions through which it can provide the understanding with representations. But the synthetic aspect of the imagination belongs to the spontaneity of the understanding, which is a determining activity rather than being determinable like sensibility. And since this a priori synthesis can determine sense according to the unity of apperception, the imagination determines sensibility in that it synthesizes its representations. So now the synthesis of imagination is the understanding acting upon sensibility. The synthesis of reproduced representations along with incoming empirical intuitions is called the productive imagination. The synthesis of the reproductive imagination, or reproduced representations from memory, is subject to the laws of association.

Kant diverts the attention of the B Deduction in this second half of §24 and the whole of §25 to clarify a possible paradox in the definition of inner sense, or how inner sense allows consciousness of only how we appear to ourselves, but not as we are in ourselves. As we intuit ourselves as we are inwardly affected through a succession of states, i.e., through time. But what determines inner sense and brings it to apperception is the understanding. And the understanding combines the intuitions in inner sense. Here, Kant draws a parallel between the relationship between outer sense being arranged by us in space and inner sense being arranged by us in time. We can only intuit objects insofar as we are externally affected, similarly, we can only intuit ourselves insofar as we are affected by ourselves. Kant then returns to his former point, that because we can only receive ourselves as appearances in time, the subject we can cognize is only as appearance, and not in itself.

However, through the synthetic unity of apperception, since it is only a form of possible cognition, through it I am not conscious of myself as appearance, nor as something in itself. I am conscious of myself only in the sense “that I am” as a pure form of synthesis. Therefore, for existence to be determined, this pure form be able to work with manifold given through inner intuition. Similarly, I only have cognitions of myself as appearance.

Now Kant moves back to the applicability of the categories. Here he asks: how the categories can cognize a priori whatever we intuit through our senses? And to cognize them concerns not the form the intuitions take in space and time, but the laws we supply in combining them. Here, he introduces perception. Perception becomes possible only when the manifold is synthesized into an empirical intuition where perception is consciousness of that very intuition.
From here, the syntheses of outer and inner intuition as appearances must always conform to the conditions of space and time. Thereby, space and time are not only forms of intuition but are intuitions themselves when they are synthesized from a manifold.

Now that we’ve further justified the necessity of intuitions for the categories, Caimi’s question remains. How do we reconcile the alien nature of the manifold with the conditions that the categories ascribe? Does that nature have to obey the conditions we supply? How do the categories a priori combine the manifold of nature without getting the combination from nature? Kant tries to solve this by again stating appearances only exist for the subject’s senses, and not in themselves. So, the conditions pertain to the subject insofar as that being has capacities for understanding. Appearances themselves aren’t subject to the laws except when they are prescribed from beings with capacities for understanding and, therefore synthesis. And imagination unifies the manifold of sense intuition, the imagination depends on understanding as supplying the unifying power. Perception depends on the synthesis of the given manifold into an intuition, and the synthesis of what is given from sense intuition depends on the synthetic unity of apperception, therefore, the categories. So, as long as we maintain the appearance/things-in-themselves distinction, we can reconcile the conditions of the subject having objective validity if it remains with appearances and does not concern the things-in-themselves.

Author's Note: This edition exists without footnote citations. This was for the class "History of Modern Philosophy".

Works Cited:
Caimi, Mario, María Caimi, and Pablo Muchnik. Kant’s B Deduction. Newcastle upon
Tyne: Cambridge Scholars, 2014.
Conant, James. “Why Kant Is Not a Kantian.” Philosophical Topics 44, no. 1 (2016): 75–125.
https://doi.org/10.5840/philtopics20164417.
Kant, Immanuel. Critique of Pure Reason. Translated by Paul Guyer and Allen W. Wood.
Cambridge University Press, 2016.

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