The Limits of Sense and Reason: A Line-By-Line Critical Commentary on Kant’s “Critique of Pure Reason,” #1.

By Robert Hanna



[I] was then making plans for a work that might perhaps have the title, “The Limits of Sense and Reason.” I planned to have it consist of two parts, a theoretical and a practical. The first part would have two sections, (1) general phenomenology and (2) metaphysics, but this only with regard to its method. (Letter to Marcus Herz, 21 February 1772 [C 10: 129])


Immanuel Kant’s Critique of Pure Reason, aka Kritik der reinen Vernunft, aka “the first Critique,” and also “CPR” for short, is the single most brilliant, difficult, and important book in modern philosophy.

The CPR was first published in 1781 (the A edition), followed six years later by a revised second edition (the B edition) in 1787.

Whole libraries could be filled with the secondary literature — books and essays — published on the first Critique, since its explosive appearance on the philosophical scene in the twilight decades of the 18th century.

Correspondingly, during the 238 years since the publication of the A edition, the impact of the CPR, via Kant’s comprehensive Critical Philosophy, has steadily deepened, increased, ramified, and widened, in three directions:

first, as a positive source for foundational work in metaphysics, epistemology, philosophy of mind, ethics, aesthetics and the philosophy of art, philosophical anthropology, the philosophy of religion and philosophical theology, political philosophy, the history and philosophy of the formal and natural sciences, and the philosophy of nature,

second, as a negative foil for all alternative developments in those basic philosophical subjects, since all philosophers in the post-Kantian era, whether pro-Kant, anti-Kant, or officially Kant-neutral, must define themselves and their work in relation to Kant and the Critical Philosophy, and

third, as a broad, deep, and powerful sociocultural force, under the much-controverted rubric of enlightenment.

Indeed, the impact of the CPR, via the larger Critical Philosophy and post-Kantian enlightenment thinking, is now truly cosmopolitan, hence worldwide, and also by no means restricted to what Schopenhauer in the mid-19th century so sarcastically and presciently called “university philosophy,”[i] that is, professional academic philosophy.

Hence Kant’s philosophical thinking and writing are fully and globally in the real world, and thereby woven as efficaciously and tightly into the warp and woof of modern life as real philosophy can ever be.

By “real philosophy” I mean authentic, serious philosophy, as opposed to inauthentic, superficial philosophy.

Correspondingly, my own metaphilosophical view about the CPR in particular and the Critical Philosophy in general is this:

Like all philosophers Kant sometimes errs, or anyhow nods. But we respect him most by critically noting and then setting aside his slips, and by promoting his deepest and most powerful doctrines…. Kant’s Critical Philosophy is fully worth studying, critically analyzing, charitably explicating, defending, and then independently developing in a contemporary context. This is because, in my opinion, more than any other single-authored body of work in modern philosophy the Critical Philosophy most doggedly pursues and most profoundly captures some non-trivial fragment of the honest-to-goodness truth about rational human animals and the larger natural world that surrounds them.[ii]

Lying behind and scaffolding those claims, my view about the relationship between contemporary philosophy and the history of philosophy is based on what I call The No-Deep-Difference Thesis:

There is no fundamental difference in philosophical content between the history of philosophy and contemporary philosophy.[iii]

In other words, in doing contemporary philosophy one is thereby directly engaging with the history of philosophy, and in doing the history of philosophy one is thereby directly engaging with contemporary philosophy.

There is no fundamental difference in philosophical content between philosophy that was thought, spoken, written, or published 2000 or 200 or 20 years ago, or 20 months ago, and philosophy that was thought, spoken, written, or published 20 weeks or 20 days or 20 minutes or 20 seconds ago.

In particular, then, The No-Deep-Difference Thesis licenses an unfettered philosophical freedom to create new philosophy, the philosophy of the future, and to interpret old or contemporary philosophy, the philosophy of the past and the philosophy of the present, without paying any attention whatsoever to supposedly uncrossable conceptual borders between philosophy’s past, present, and future, that we might have been indoctrinated into believing, by virtue of graduate school training and professional academic ideological discipline.[iv]

In accordance with my metaphilosophical view of the Critical Philosophy and The No-Deep-Difference Thesis, then, the aim of The Limits of Sense and Reason, henceforth LST, is to combine a complete and fully detailed critical commentary on the CPR — line-by-line, and sometimes even word-by-word — with a charitable, creative philosophical reconstruction of Kant’s ideas, using as little scholarly apparatus as possible.

In the interests of full disclosure, I had better also lay my first-order philosophical cards on the table right here at the outset, and provide a preliminary sketch of what my philosophical reconstruction of the first Critique will look like.

It is motivated by a contemporary Kantian theory of human cognition and action that I’ve dubbed Kantian Non-Conceptualism.[v]

Elsewhere, I’ve spelled out and defended Kantian Non-Conceptualism in full detail.[vi]

So for my present purposes, I will simply state it, in order to be able then to deploy it throughout the rest of LSR.

The thesis of Non-Conceptualism about mental content says that not all mental contents in the intentional or representational acts or states of minded animals are necessarily or constitutively determined by their conceptual capacities, and that at least some mental contents are necessarily or constitutively determined by their non-conceptual capacities.[vii]

Non-Conceptualism is sometimes, but not always, combined with the further thesis that non-conceptual capacities and contents can be shared by rational human animals, non-rational human minded animals (and in particular, infants), and non-human minded animals alike.

But in any case, Non-Conceptualism is directly opposed to the thesis of Conceptualism about mental content, which says that all mental contents are necessarily or constitutively determined by minded animals’ conceptual capacities.[viii]

Conceptualism is also sometimes, but not always, combined with the further thesis that the psychological acts or states of infants and non-human minded animals lack mental content.

Now in a nutshell, Non-Conceptualism says that our cognitive access to the targets of our intentionality is neither always nor necessarily mediated by concepts, nor sufficiently determined or constituted by concepts, which is the concept-independence of non-conceptual content, and therefore that our cognitive access to the targets of our intentionality is sometimes wholly unmediated by concepts, or altogether concept-free, which is the concept-autonomy of non-conceptual content; and Conceptualism says that our cognitive access to the targets of our intentionality is always and necessarily mediated by concepts, and indeed also sufficiently determined or constituted by concepts.

Here, then, are the fundamental philosophical questions that are being asked in the debate about non-conceptual content:

Can we and do we sometimes cognitively encounter other things and ourselves directly and non-discursively, hence non-intellectually or sensibly (Non-Conceptualism), or must we always cognitively encounter them only within the framework of discursive rationality, hence intellectually or discursively (Conceptualism)?

Are we, as rational animals, essentially different from other kinds of animals (Conceptualism), or do we share at least some minimally basic mental capacities with all minded animals (Non-Conceptualism)?

And finally:

Is a thoroughly intellectualist and “discursivity first” view of the rational human mind (Conceptualism) correct, or by sharp contrast is a non-intellectualist and “sensibility first” view of the rational human mind (Non-Conceptualism) correct?

I think that the sensibility first view of the rational human mind is the correct one.

It is also important to note that whereas Conceptualism is of necessity a form of content-monism, which says there is one and only kind of intentional or representational content (sometimes, however, combined with capacity-dualism, which says that there are two essentially different basic kinds of cognitive capacities), by contrast Non-Conceptualism can be, and usually is, a form of content-dualism, which says that there are two essentially different kinds of intentional or representational content, and if so, then it is always a form of capacity-dualism too.

Correspondingly, the version of Non-Conceptualism that I defend, Strong Kantian Non-Conceptualism, is not only content-dualist but also capacity-dualist.

As a sub-species of Non-Conceptualism, Strong Kantian Non-Conceptualism says this:

The human or non-human capacity for sensibility not only generates empirical intuitions and a priori intuitions that autonomously and independently provide objectively valid representational contents, but also, by means of these autonomous and independent, essentially non-conceptual cognitions, the faculty of sensibility contributes directly to the justification of epistemic and practical beliefs, by virtue of inherently normative and proto-rational factors that it builds into the essentially non-conceptual content of intuitions.

More precisely, however, Strong Kantian Non-Conceptualism is the following three-part doctrine:

(i) mental acts or states in minded animals have representational content whose semantic structure and psychological function are essentially distinct from the structure and function of conceptual content,

(ii) the specific psychological function of essentially non-conceptual content is to guide conscious intentional desire-driven body movements for the purposes of cognition and practical agency, and

(iii) the semantic structures of essentially non-conceptual content are equivalent to Kant’s spatiotemporal forms of intuition, including their representational roles as “formal intuitions” (CPRB136), and also as non-empirical schemata or “mental models” generated by the “figurative synthesis of the imagination” (CPR B151–156 A137–147/B176–187).

According to Kantian Conceptualism, human minds are basically intellectual in character, having nothing inherently to do with the embodied, sense-perceiving, affective, desiring, animal side of human nature.

By contrast, according to Strong Kantian Non-Conceptualism, human minds are basically bound up with the embodied, sense-perceiving, affective, desiring, animal side of human nature, and therefore are not basically intellectual in character: on the contrary, the intellectual capacities of the human being constitutively presuppose, and are thereby grounded on and built on top of, the non-intellectual capacities, the sensible capacities.

In this way, my reading of the first Critique in particular, and of the Critical Philosophy in general, is what I call “the sensibility first reading,” grounded on Strong Kantian Non-Conceptualism.

If I am correct about Strong Kantian Non-Conceptualism, then it is also a deliciously ironic fact, because Kant is almost universally regarded as the founding father of Conceptualism and the nemesis of Non-Conceptualism.

York Gunther articulates the standard view perfectly:

In his slogan, “Thoughts without content are empty, intuitions without concepts are blind,” [CPR A51/B75] Kant sums up the doctrine of conceptualism.[ix]

Nevertheless, I think that Kant is most accurately regarded not only as the founder of Conceptualism but also, and perhaps even more importantly, as the founder of Non-Conceptualism in general and Strong Kantian Non-Conceptualism in particular.[x]

So for all these reasons, and others equally compelling, flowing from his practical and moral philosophy,[xi] I think that the best overall reading of Kant’s philosophy of mind, metaphysics, and epistemology, and also of his practical and moral philosophy, is the Sensibility First reading.

In turn, Kant’s double role as the founder of Conceptualism and (Strong Kantian) Non-Conceptualism alike makes perfect sense when we also realize that he was the first content-dualist and capacity-dualist in modern philosophy, by postulating the fundamental difference between the human capacity for conceptualization and thinking, “understanding” or Verstand on the one hand,and the human capacity for generating directly referential intuitions or Anschauungen, “sensibility” or Sinnlichkeit, on the other hand.

In this way he significantly distinguishes himself from classical Rationalists and classical Empiricists alike, who were (and in a contemporary context, are) defenders of capacity monism, which says that there is one and only one basic kind of cognitive capacity, namely reason and sensory experience respectively.

Here are five Kant-texts that, taken collectively, strongly confirm my claim that Kant is the Ur-Non-Conceptualist and a Strong Kantian Non-Conceptualist alike.

Objects can indeed appear to us without necessarily having to be related to the functions of the understanding. (CPR A89/B122, underlining added)

Appearances could after all be so constituted that the understanding would not find them in accord with the conditions of its unity.… Appearances would nonetheless offer objects to our intuition, for intuition by no means requires the functions of thinking. (CPR A90/B123, underlining added)

That representation which can be given prior to all thinking is called intuition. (CPR B132, underlining added, boldfacing in the original)

The manifold for intuition must already be given prior to the synthesis of the understanding and independently from it. (CPR B145, underlining added)

Concept differs from intuition by virtue of the fact that all intuition is singular. He who sees his first tree does not know what it is that he sees. (VL 24: 905, underlining added)

In my opinion, then, what Kant’s famous slogan about blind intuitions and empty thoughts actually means is that intuitions and concepts must always be combined together for the special purpose of making objectively valid “judgments of experience” (Erfahrungsurteile).

But outside that context, it is also perfectly possible to have directly referential intuitions without concepts (“blind intuitions,” for example, a pre-linguistic infant’s first cognitive encounter with a tree), and also to have thinkable concepts without intuitions (“empty concepts,” for example, concepts of things-in-themselves or noumena).

Indeed, it is precisely the fact of blind intuitions, whose semantic structure and psychological function are essentially distinct from the semantic structure and psychological function of concepts, that drives Kant’s need to argue in the first Critique’s B edition Transcendental Deduction that all and only the objects of actual or possible human experience are necessarily conceptualized or conceptualizable under the pure concepts of the understanding or categories, and necessarily constrained by the transcendental laws of a pure science of nature.

Otherwise, blind intuitions might pick out what I have called “rogue objects” of human experience that are either contingently or necessarily unconceptualizable, and nomologically intractable — causal deviants, and rude violators of the general deterministic (or, although Kant himself would not have recognized such things, general indeterministic) causal laws of nature.[xii]

Timothy Williamson calls these rogue objects “elusive objects,” and makes essentially the same critical Kantian point I am making here — namely, that the scope of the Transcendental Deduction is inherently constrained by the possibility of rogue or elusive objects — although he does so in the context of criticizing John McDowell’s Conceptualism:

For objects, McDowell’s claim that the conceptual is unbounded amounts to the claim that any object can be thought of. Likewise for the sort of thing that can be the case: the claim is, for example, that whenever an object has a property, it can be thought, of the object and the property, that the former has the latter…. McDowell’s argument in any case seems to require the premise that everything (object, property, relation, state of affairs, …) is thinkable. That premise is highly contentious. What reason have we to assume that reality does not contain elusive objects, incapable in principle of being individually thought of?… Although elusive objects belong to the very same ontological category of objects as those we can single out, their possibility still undermines McDowell’s claim that we cannot make “interesting sense” of the idea of something outside the conceptual realm …. We do not know whether there are actually elusive objects. What would motivate the claim that there are none, if not some form of idealism very far from McDowell’s intentions? We should adopt no conception of philosophy that on methodological grounds excludes elusive objects.[xiii]

In view of all that, then, first, I hold the historico-philosophical thesis that Kant’s theory of concepts and judgment in the Transcendental Analytic, if correct, provides foundations for Conceptualism.

But equally and oppositely, second, I also hold the historico-philosophical thesis that Kant’s theory of intuition in the Transcendental Aesthetic, if correct, provides foundations for Strong Kantian Non-Conceptualism, and also inherently constrains what Kant argues in the Transcendental Analytic.


By saying that I will be “using as little scholarly apparatus as possible” in LSR, I meant that I have decided to restrict references to or discussions of the massive secondary literature on Kant to a bare minimum, and always inside the footnotes.

At the same time, however, in the main text itself, I do refer to relevant works by other important philosophers or non-philosophers, and also to relevant facts about Kant’s life, as well as to other philosophical works by Kant.

As to CPR-commentaries: There have previously been four major full-length commentaries on the first Critique, two in German and two in English — authored, respectively, by Hans Vaihinger, Erich Adickes, Norman Kemp Smith, and H.J. Paton.

The last of these was published in 1936, 83 years ago.

So it’s high time for another one to appear.

— Of course, given its aim, The Limits of Sense and Reason is an infinite work-in-progress.

Therefore, for the time being at least, I have decided to publish it here on Against Professional Philosophy, week-by-week.

It will be interesting to see how much I am able to get done over the next 20 or so years: provided, of course, that I am lucky enough to live, and remain reasonably healthy and sane, that long.


[i] A. Schopenhauer, “On University Philosophy,” in A. Schopenhauer, Parerga and Paralipomena: Short Philosophical Essays, vol. 1, trans. S Roehr and C. Janaway (Cambridge: Cambridge Univ. Press, 2014), pp. 125–176.

[ii] R. Hanna, Kant, Science, and Human Nature (Oxford: Clarendon/Oxford Univ. Press, 2006), p. 7, also available online in preview, HERE.

[iii] See R. Hanna, “Life-Changing Metaphysics: Rational Anthropology and its Kantian Methodology,” in G. D’Oro and S. Overgaard (eds.), The Cambridge Companion to Philosophical Methodology, (Cambridge: Cambridge Univ. Press, 2017), pp. 201–226, section 3, also available online in preview, HERE.

[iv] See, for example, R. Hanna, “Back to Kant: Teaching the first Critique as Contemporary Philosophy,” APA Newsletter on Teaching Philosophy 8 (2009): 2–6, available online at URL = <>; and J. Schmidt, Disciplined Minds (Lanham, MD: Rowman & Littlefield, 2000).

[v] See, for example, R. Hanna, “Kant and Nonconceptual Content,” European Journal of Philosophy 13 (2005): 247–290; R. Hanna, “Kantian Non-Conceptualism,” Philosophical Studies 137 (2008): 41–64; R. Hanna, “The Myth of the Given and the Grip of the Given,”DIAMETROS 27 (March 2011), at URL = <>; R. Hanna, “Beyond the Myth of the Myth: A Kantian Theory of Non-Conceptual Content,” International Journal of Philosophical Studies 19 (2011): 321–396; and R. Hanna and M. Chadha, “Non-Conceptualism and the Problem of Perceptual Self-Knowledge,” European Journal of Philosophy 19, 2 (June 2011): 184–223.

[vi] R. Hanna, Cognition, Content, and the A Priori: A Study in the Philosophy of Mind and Knowledge (THE RATIONAL HUMAN CONDITION, Vol. 5) (Oxford: Oxford Univ. Press, 2015),ch. 2, also available online in preview, HERE.

[vii] See, e.g., Bermúdez, J. and Cahen, A. “Nonconceptual Mental Content,” in E.N. Zalta (ed.), The Stanford Encyclopedia of Philosophy (Fall 2015 Edition), available online at URL = <>; G. Evans, Varieties of Reference (Oxford: Clarendon/Oxford Univ. Press, 1982), esp. chs. 4–6; and Y. Gunther (ed.), Essays on Nonconceptual Content (Cambridge: MIT Press, 2003).

[viii] See, for example, J. McDowell, Mind and World (Cambridge: Harvard Univ. Press, 1994); J. McDowell, Having the World in View (Cambridge, MA: Harvard Univ. Press, 2009); S. Sedivy, “Must Conceptually Informed Perceptual Experience Involve Non-conceptual Content?,” Canadian Journal of Philosophy 26 (1996): 413–431; and B. Brewer, Perception and Reason (Oxford: Oxford Univ. Press, 1999).

[ix] Y. Gunther, “Introduction,” in Gunther (ed.), Essays on Nonconceptual Content, pp. 1–19, at p. 1.

[x] Hanna, “Kant and Nonconceptual Content.”

[xi] See, for example, R. Hanna, Deep Freedom and Real Persons: A Study in Metaphysics (THE RATIONAL HUMAN CONDITION, Vol. 2) (New York: Nova Science, 2018), sections 3.3 and 3.4, also available online in preview, HERE.

[xii] See R. Hanna, “Kant’s Non-Conceptualism, Rogue Objects, and the Gap in the B Deduction,” International Journal of Philosophical Studies 19 (2011): 397–413; and “Kantian Madness: Blind Intuitions, Essentially Rogue Objects, Nomological Deviance, and Categorial Anarchy,” Contemporary Studies in Kantian Philosophy 1 (2016): 44–64, available online at URL = <!Kantian-Madness-Blind-Intuitions-Essentially-Rogue-Objects-Nomological-Deviance-and-Categorial-Anarchy/cmbz/576018190cf2c6c572641509>.

[xiii] T. Williamson, The Philosophy of Philosophy (Oxford: Blackwell, 2007), pp. 16–17.


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Mr Nemo

Formerly Captain Nemo. A not-so-very-angry, but still unemployed, full-time philosopher-nobody.