Kant repeatedly claims his critical enterprise is analogous to pure general logic (PGL) in embodying the self-knowledge of reason. I argue that PGL is self-knowledge in the sense that its claims are epistemically grounded in pure apperception, which yields insight into the form of thinking in general. Kant’s critical epistemology, as distinct from his critical metaphysics, is self-knowledge in an analogous sense: It is an apperceptively grounded inquiry into the form of all a priori thought about objects. I develop an account of the purity, generality, and formality of PGL, which I then leverage into an outline of the apperceptive method that underwrites Kant’s faculty psychology. This novel account of Kant’s critical method distinguishes it from the analytical but dogmatic method of Wolff and the reflective but empirical methods of Locke and Tetens.

I reconstruct the preliminary arguments of the Transcendental Aesthetic, which provide the criteria of on which Kant’s central arguments will turn. Kant characterizes intuition as (i) object-giving, (ii) immediate, (iii) affection-dependent representation containing (iv) a matter of sensation that can be distinguished from (v) an a priori form. I explain Kant’s curiously teleological claim that all thought “aims at” intuition in terms of his “baseline conception” of intuition as providing nonintellectual grounds of truth: This is what it means for intuition to be object-giving. I then argue that Kant’s theory of discursive marks entails that object-giving representations must be immediate. Further, the intuition paired with a discursive intellect must be receptive (i.e. affection dependent). These claims can be justified via pure apperception. What cannot be is Kant’s characterization of intuition as sensible. But I show that Kant’s form/matter distinction and his subsequent arguments require only the receptivity of intuition, not its sensory embodiment. The chief doctrines of the Aesthetic can be justified via pure apperception, as part of a top-down approach to intuition.

I develop an account of Kant’s technical notion of “exposition” and, in particular, “metaphysical” exposition. This involves explaining his distinction between concepts that are “made” and those that are “given,” as well as his murky notion of “original acquisition.” I then turn to Kant’s account of exposition as conceptual analysis. I argue that apperceptive reflection is the principal vehicle of conceptual analysis and, thus, the nervus probandi of Kant’s arguments in the Expositions. This yields a general picture of the Expositions as advancing the critical project of reason’s self-knowledge. An attractive consequence of my account en passant is that the discussion of original acquisition provides a novel and tidy explanation of the much-discussed distinction between formal intuition and the form of intuition in terms of the tripartite Aristotelian distinction between first potentiality, second potentiality (first actuality), and second actuality.

Sense perception is a paradigm of Kantian intuition. Yet Kant also makes intuition responsible for representing mathematical infinities, whereas sense perception is manifestly finite. Why assign such contrary cognitive achievements to a single capacity? I trace this doctrinal heterodoxy to Kant’s revolutionary methodology: viz. his faculty psychology. Unlike his predecessors, Kant bases his claims about the mind not on empirical observation nor on metaphysical reasoning but on apperceptive reflection. Performing an act of intellect constitutively involves the ability to represent oneself as doing so. And the latter ability requires one to possess (albeit implicitly and unreflectively) a concept of the relevant act-type. Kant’s faculty psychology consists in making these concepts explicit, analyzing them, and distinguishing faculties via the acts (cognitive functions) they enable. I argue that the intellect’s apperceptive grasp on the functions it does perform includes an implicit conception of those cognitive functions that it presupposes but cannot perform. These are therefore assigned to a distinct, non-intellectual capacity that serves as the intellect’s cognitive partner in generating knowledge. The intellect’s knowledge of itself thus includes an indirect knowledge of the intellect’s Other. This “top-down” approach to intuition explains Kant’s doctrinal heterodoxy. Infinite complexity must be represented intuitively because it is essential to our (Newtonian) knowledge of the world yet cannot be accounted for by the discursive spontaneity of our intellect.

The final two Metaphysical Expositions argue that our original representation of space must be intuitive. I draw some surprising connections between Kant’s discussion and Leibniz’s account of the continuum. These connections indicate that the point of Kant’s analysis of <space> is to show that our original representation of space is infinitely complex in content. Since no discursive representation can be infinitely complex, our concept <space> cannot derive its content from discursive spontaneity. Its content must rather be given to the mind in order to be thought at all and thus originates in receptive intuition. Kant’s argument does not hinge on the singularity or holistic structure of space, as many hold, but on its infinite complexity and consequent givenness. I develop a novel account of the discursivity of conceptual representation that preserves the validity of Kant’s argument, defend Kant’s account of the infinity of space against prominent objections, and finally indicate how Kant’s argument entails the singularity of intuition (rather than presupposing it).

I argue that the sensibility/understanding distinction announced at the end of Kant’s Introduction to the Critique can be justified via pure apperception. I first defend an account of the analytic/synthetic distinction, arguing that analytic judgments articulate intellectual grounds of truth. Synthetic judgments, then, are based on nonintellectual grounds of truth. This provides Kant’s “baseline conception” of receptive intuition as a capacity for representing nonintellectual grounds of truth. This is a “top-down” approach to intuition: a characterization of intuition not in terms of its intrinsic properties but in terms of a prior account of the intellect and its cognitive needs. I then argue that this version of the analytic/synthetic distinction follows from the idea that judgment must track the truth – an idea that is available to us via pure apperception. Thus, Kant’s baseline conception of intuition, as expressed in the sensibility/understanding distinction, can be justified via pure apperception.

Interpreters often cite Kant’s Stufenleiter of representations (A320/B376) as providing a “definition” of intuition. This misunderstands the peculiar logic of Porphyrian classification, which I clarify by reviewing its history. Porphyrian trees do offer conceptual analyses, I argue, but do not purport to provide a uniquely correct, much less exhaustive, account of the analysand. Different orderings of differentia, as well as different differentia, are often possible. Which terms and which kinds of terms appear as differentia in the analysis depends on the goals and constraints on the philosophical inquiry to which the analysis contributes. It is therefore illegitimate to extract a “definition” of intuition from Kant’s Stufenleiter. First, its analysis targets <idea of reason> (not <intuition>), and, second, it does not purport to give a uniquely correct account of that concept (much less of <intuition>), as a definition must.

I provide a Stufenleiter of human intuition that systematizes Kant’s discussions. Starting with intuition überhaupt, as object-giving representation, I distinguish spontaneous from receptive intuition. I divide receptive intuition into sensible and non-sensible; and divide sensible intuition into inner and outer sense, under which our human varieties of temporal and spatial intuition fall as instances (not species). This chapter offers detailed accounts of givenness and of cognitive spontaneity (the other differentia are addressed in Chapter 8). I argue that givenness, the fundamental criterion of intuition überhaupt, involves securing both (i) the existence of the object and (ii) thought’s cognitive access to it. One might worry that these functions could come apart. I address this worry by developing a novel interpretation of spontaneity and its opposite, receptivity. As applied to representations, I argue, these notions are fundamentally epistemic and explanatory. This is why the functions cannot come apart and why a representation that performs one function spontaneously (or, as the case may be, receptively) must also perform the other spontaneously (or receptively).

I continue explicating my Stufenleiter by distinguishing receptivity from sensibility, which are often conflated in the literature. I argue that the preestablished harmony theories of Leibniz and Crusius, as well as the “hyperphysical influx” Kant ascribes to Plato, involve receptive but non-sensible modes of intuition. I identify significant and underappreciated puzzles afflicting Kant’s notion of sensible affection: Kant has no account of how material objects can affect an immaterial mind, nor any account of how an immaterial mind can sensibly affect itself. I conclude by observing that many of the distinctions I discuss, such as the receptivity/sensibility distinction, track different levels of abstraction and that this can have significant consequences for motivating interpretations. Emphasizing sensibility often motivates phenomenological interpretations (Parsons), whereas semantic or “logical” readings (Hintikka) typically emphasize receptivity. I illustrate the fruitfulness of this diagnosis by distinguishing three different conceptions of the singularity of intuition, each associated with a different level of abstraction: receptive, sensible, and human.