In the opening sentences of the Transcendental Aesthetic, Kant writes that intuition is that through which cognition relates immediately to objects (A19/B33). He then adds that intuitions belong to the faculty of sensibility, which enables objects to be given to us, while the understanding is the faculty of concepts and thought (A19/B33). Thus, at the very outset of the Critique, Kant appears simply to stipulate that sensibility is the faculty of object-giving intuitions, while understanding is the faculty of concepts, a stipulation that proves fundamental to his arguments for transcendental idealism. Given this, a pressing question concerns how Kant justifies his characterizations of sensibility and understanding. On what grounds does Kant assert that intuitions and concepts have the features he attributes to them, and can Kant’s rationalist opponents simply insist that the understanding alone is a source of cognition of objects?
In his excellent new book, Daniel Smyth sheds new light on these questions by offering a comprehensive account of Kant’s conception of intuition and his argumentative strategy in the Transcendental Aesthetic. Smyth’s central contention is that Kant develops a functionalist, “top-down” approach to intuition, which is to say that he starts with an independent account of the intellect’s capacities and then argues that these require a complementary faculty of intuition to explain representations that the intellect alone cannot secure. In particular, Smyth argues, Kant holds that only a faculty of intuition can account for our representations of the infinite. Thus, against interpretations that take Kant to start with empirical or phenomenological claims about intuitive representation, Smyth reads Kant as inferring to claims about intuition from observations about how our discursive intellects function. More specifically, in Smyth’s view, pure apperception justifies Kant’s claims about our discursive understanding, which in turn yield indirect knowledge of sensibility and the nature of intuition. Seen in this light, Kant’s opponents should be able to reach all the conclusions that Kant does by employing pure apperception to clarify the nature and limits of our discursive understanding, and Kant’s arguments are not question-begging after all.
The book divides into two parts: chapters 1–5 develop the “top-down” argument for the existence and structure of sensible intuition, while chapters 6–8 reconstruct a conceptual Stufenleiter of intuition revealing how different features of intuition emerge at different levels of abstraction.
While I will raise some concerns about the details of Smyth’s account, let me say at the outset that this is an outstanding contribution to Kant scholarship. It is philosophically ambitious, exceptionally clear, and densely argued in the best sense: it rewards close reading without becoming opaque, and the view it develops is, to my knowledge, genuinely novel. Smyth notes at various junctures that nearby ideas have appeared elsewhere in the literature, but no other work of which I am aware lays out the position Smyth develops with such care and depth. The book is also a model of scholarly responsibility; it is well-grounded in the primary texts, attentive to historical context, and engaged with the most relevant secondary literature. On the whole, The Boundlessness of Sense is an intellectually satisfying and historically informed piece of scholarship that should be essential reading for anyone interested in the Transcendental Aesthetic or Kant’s theory of intuition.
As for the book’s argumentative structure, chapter 1 argues that Kant’s method in the Critique parallels that of pure general logic (PGL). Both are exercises in Selbsterkenntnis, which articulate the constitutive norms of the intellect, but whereas PGL treats the formal norms governing all thinking whatsoever (15), critique isolates the norms involved in a priori cognition of objects (22). Both disciplines make their claims by appealing to the intellect’s reflective grasp of its own acts and norms, and it is precisely this kind of apperceptive grasp of the intellect’s own operations that Smyth argues grounds Kant’s fundamental claims about the understanding and sensibility in the Critique.
Chapter 2 then argues for the striking claim that the distinction between understanding and sensibility is a “direct corollary” of the distinction between analytic and synthetic judgment (55). According to Smyth, whereas the intellect as the faculty of concepts grounds the truth of analytic judgments (51), synthetic judgments presuppose access to grounds of truth that are not contained in the intellect or its concepts. Thus, synthetic judgments presuppose a receptive faculty of intuition. Intuition on this account is defined functionally as “a cognition-enabling capacity distinct from the understanding that provides us epistemic access to grounds of truth for synthetic propositions” (55). And importantly, all of this is known to us through pure apperception (64). In other words, via our apperceptive grasp of our faculty of understanding we can infer to a faculty of intuition defined solely in terms of its cognitive role: it is that which “gives” us thought-independent grounds of truth.
Chapter 3 turns to the preliminary sections of the Transcendental Aesthetic, whose core claims Smyth likewise interprets as grounded in pure apperception. Because the discursive intellect is essentially spontaneous, Smyth argues, and because it cannot on its own secure thought-independent grounds of truth, we must possess a receptive capacity for immediate intuition (90). Smyth emphasizes that this argument is independent of any empirical or phenomenological considerations, and receptivity rather than sensation is the crucial feature of intuition in the Aesthetic (93). Human intuition is indeed sensible in Smyth’s view, but claims of the Aesthetic do not depend on this fact, and all the heavy lifting is done by the notion of receptivity (99).
Chapter 4 reconstructs the method of the Metaphysical Exposition for space (ME), which Smyth treats as an apperceptive analysis of the concept <space>. According to Smyth, the ME’s aim is to extract conceptual marks (such as unity, infinite divisibility, and holistic structure) that reflect the form of our capacity for intuition (120), and its method is to proceed by reflection on our competent use of the concept <space> rather than on the content of experience (126–127). Kant’s ultimate conclusion is that the key marks of <space> could only derive from the form of receptive intuition. Thus, per Smyth, the ME properly understood is an exercise in conceptual analysis, which shows that <space> must be grounded in the essential structure of our capacity for intuition (131).
Chapter 5 defends what Smyth takes to be Kant’s central argument in the Aesthetic: our original representation of space is infinitely complex and therefore cannot be discursive (132). As Smyth argues, discursive concepts are finitely complex due to their classificatory structure: their content depends on comparisons among finitely many instances (167). In contrast, the representation of space exhibits continuity and boundlessness, features that imply infinite complexity. But given this, the representation of space must have its origin in receptive intuition, not the intellect (153). Kant’s method here is once again apperceptive and structured in a top-down way. Kant infers not from phenomenological considerations but rather from observations about the role that <space> plays in synthetic cognition; since discursive spontaneity is insufficient to account for our representation of space’s structure, that structure must be given in sensible intuition (161).
Chapters 6–8 shift to taxonomy, offering a Stufenleiter of types of intuition distinguished by increasing levels of determination. At the most abstract level, the general concept of intuition is defined by its cognitive function: it gives the mind access to thought-independent grounds of truth (199–202). This general capacity then divides into spontaneous (intellectual) and receptive species, depending on whether its operations are grounded wholly in the subject’s rational powers (213). And receptivity itself is further distinguished from (i) sensibility as a species of receptivity and (ii) sensory affection as a species of sensibility. Features like singularity and spatiotemporality are then understood not as marks of all intuition per se but rather as features that emerge at specific levels of abstraction (227). Smyth’s discussion of singularity illustrates this especially clearly: non-generality belongs to receptive intuition, concreteness to sensible intuition, and spatiotemporal individuation to our specifically human form (242).
Much more can be said about each of Smyth’s chapters, and these summaries do not do justice to the breadth and depth of Smyth’s arguments. For now, however, let me turn to three issues that strike me as worthy of further attention.
First, though Smyth’s focus is on the Transcendental Aesthetic, his claims about the intuitive origins of our infinitary representations raise interesting questions about Kant’s treatment of the infinite in the Transcendental Dialectic. There, Kant holds that reason can represent an actually infinite series of conditions as unconditioned, a claim that plays an important role in setting up the antinomy of pure reason (A417–18/B445). But as we have seen, on Smyth’s account representations of infinitary contents must be sourced in intuition. Given that Kant appears to treat the idea of an infinite totality of conditions as sourced in reason, how should a view like Smyth’s understand such representations? Must reason’s idea of an infinite unconditioned series ultimately depend on intuition? Or is there something distinctive about the way we represent such an infinite series that exempts it from the kind of argument Smyth brings to bear on space and time? These questions fall outside the scope of Smyth’s book, but they point to ways in which its central claims may bear on Kant’s account of infinity far beyond the Aesthetic.
Second, one of the more revisionary aspects of Smyth’s account is his thin notion of receptivity. For Smyth, cognitive spontaneity is defined functionally: a faculty is spontaneous if its acts can be “sufficiently accounted for by reference to features and capacities that a subject possesses merely qua cognizer, i.e., qua rational being” (204). Correspondingly, a faculty is receptive just in case it is not spontaneous. In proposing this account, Smyth explicitly severs receptivity from affection or sensation (213): to be receptive is not to be causally affected in the empirical sense but rather to be an exercise not wholly grounded in the subject’s rational nature. Thus, even divine recognition of the goodness of creation (207), the feeling of respect for the moral law (215), and formal intuition count as “receptive”. Is too much lost by severing receptivity from affection, counting as receptive many things that we would seem to want to reserve for the domain of spontaneity? Importantly, Smyth qualifies his view by noting that “it is only the object-giving aspects of human intuition that must be receptive,” and so his view “does not require that every intuition in its entirety is passively received” (99). Thus, formal intuitions can have spontaneous elements even though they count as receptive in their object-giving respects. But given his definition of spontaneity in terms of complete groundedness in the subject’s rational capacities, it is not clear how any component of a formal intuition could qualify as spontaneous; after all, its active element arises from the figurative synthesis of the imagination (B151), and this arguably is not accounted for by our rational capacities alone. Thus, readers may wonder whether the “spontaneity” at work in formal intuitions and mathematical construction—plausibly a central case motivating Smyth’s arguments—is in fact governed by a different, more complex notion of cognitive spontaneity than his own official definition permits.
Finally, one last concern I would like to raise pertains to Smyth’s understanding of givenness as an essential feature of intuition in general. Smyth presents givenness as unifying both intellectual and receptive intuition, and he glosses it partly in terms of “cognitive availability”. As he writes, “Intuitive givenness. . .involves two things: (i) the possibility of thought’s agreeing with an object (truth evaluability) and (ii) the possibility of its recognizing such agreement (cognitive availability)” (200). However, it is unclear how this notion applies in cases of unconscious sensible intuition—such as the intuitions invoked in the infinite decompositional regress of the Second Antinomy—which do not appear to be accessible to consciousness. If these are still counted as intuitions (as Smyth allows), then cognitive availability may not, after all, be a necessary feature of intuition überhaupt. Yet if it is necessary, then we appear to exclude some of Kant’s own examples of intuitive cognition. Smyth recognizes that cognitive availability is difficult for Kant to explain where the infinitary structure of intuition comes into play (201), so I am not raising a problem of which Smyth is unaware, but the issue would benefit from fuller discussion, especially given the foundational role that givenness plays in Smyth’s account.
Let me close by emphasizing again that this is an excellent book. The questions I have raised here strike me less as flaws than as indications of how much the book offers to think about, and I am confident Smyth’s work will shape future scholarship on the Critique in very fruitful ways.