Jul 12, 2021

19 min read

THE LIMITS OF SENSE AND REASON: A Line-By-Line Critical Commentary on Kant’s “Critique of Pure Reason,” #19–Kant’s Copernican Revolution as a Philosophical Abduction, The Limits of Possible Experience, Things-in-Themselves, and Practical Reason.

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])

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Previous Installments:

#1: Introduction to The Limits of Sense and Reason

#2: Bii/GW91 The Motto

#3: Aiii/Biii/GW93–97 The Dedication

#4: Avii-ix/GW99 Preface to the First (A) Edition.

#5: Axi note/GW100–101 Preface to the First (A) Edition

#6: Axi note/GW100–101 Preface to the First (A) Edition

#7: Axii-xiv/GW101–102 Preface to the First (A) Edition

#8: Axv-xvi/GW102–103 Preface to the First (A) Edition

#9: Axvi-xvii/GW103 Preface to the First (A) Edition

#10: Axvii-xx/GW103–104 Preface to the First (A) Edition

#11: Axxi-xxii/GW104–105 Preface to the First (A) Edition

#12: Bviii-ix/GW106–107 Preface to the Second (B) Edition

#13: Bix-x/GW107 Preface to the Second (B) Edition

#14: Bx-xii/GW107–108 Preface to the Second (B) Edition

#15: Bxii-xiv/GW108–109 Preface to the Second (B) Edition

#16: Bxiv-xv/GW109–110 Preface to the Second (B) Edition

#17: Bxv-xxii/GW109–113 Preface to the Second (B) Edition, Part I

#18: Bxv-xxii/GW109–113 Preface to the Second (B) Edition, Part II

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Because LSR is an ongoing and indeed infinite task, yearly installments of the book will be published in the online journal Contemporary Studies in Kantian Philosophy (CSKP).

Correspondingly, LSR, Part 1 has been published in CSKP 6 (2021): 11–109, and can be read, downloaded, or shared in .pdf HERE.

Moreover, a bibliography of Kant’s writings listed by English translations of their titles, alongside the abbreviations used for infratextual references in LSR, has been also been published in CSKP 6 (2021): 1–10, and can be read, downloaded, or shared in .pdf HERE.

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CPR TEXT Bxv-xxii/GW109–113 Preface to the Second (B) Edition

This text was quoted in its entirety in installment #17, HERE.

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COMMENTARY

(III) Kant’s Copernican Revolution as a Philosophical Abduction, the Limits of Possible Experience, Things-in-Themselves, and Practical Reason

As for objects insofar as they are thought merely through reason, and necessarily at that, but that (at least as reason thinks them) cannot be given in experience at all — the attempt to think them (for they must be capable of being thought) will provide a splendid touchstone of what we assume as the altered method of our way of thought, namely that we can cognize of things a priori only what we ourselves have put into them.* (CPR Bxviii)

* This method, imitated from the method of those who study nature, thus consists in this: to seek the elements of pure reason in that which admits of being confirmed or refuted through an experiment. Now the propositions of pure reason, especially when they venture beyond all limits of possible experience, admit of no test by experiments with their objects (as in natural science): thus to experiment will be feasible only with concepts and principles that we assume a priori by arranging the latter so that the same objects can be considered from two different sides, on the one side as objects of the senses and the understanding for experience, and on the other side as objects that are merely thought at most for isolated reason striving beyond the limits of experience. If we now find that there is agreement with the principle of pure reason when things are considered from this twofold standpoint, but that an unavaoidable conflict of reason with itself arises with a single standpoint, then the experiment decides for the correctness of that distinction. (CPR Bxviii-xix n., boldfacing in the original)

This experiment succeeds as well as we could wish, and it promises to metaphysics the secure path of a science in its first part, where it concerns itself with concepts a priori to which the corresponding objects appropriate to them can be given in experience. For after this alteration in our way of thought we can very well explain the possibility of cognition a priori, and what is still more, we can provide satisfactory proofs of the laws that are the a priori ground of nature, as the sum total of objects of experience — which were both impossible according to the earlier way of proceeding. But from this deduction of our faculty of cognizing a priori in the first part of metaphysics, there emerges a very strange result, and one that appears very disadvantageous to the whole purpose with which the second part of metaphysics concerns itself, namely that with this faculty we can never get beyond the limits of possible experience, which is nevertheless precisely the most essential occupation of this science. But herein lies just the experiment providing a decisive test (Gegenprobe) of the truth of the result of that first assessment of our rational cognition a priori, namely that such cognition reaches appearances only, leaving the thing itself in itself (Sache an sich selbst) as real (wirklich) for itself, but uncognized by us. For that which necessarily drives us to go beyond the limitsof experience and all appearances is the unconditioned, which reason necessarily and with every right demands in things-in-themselves (Dingen an sich) for everything that is conditioned, thereby demanding the series of conditions as something completed. Now if we find that on the assumption that our cognition conforms to the objects as things-in-themselves, the unconditioned cannot be thought at all without contradiction, but that on the contrary, if we assume that our representation of things as they are given to us does not conform to these things as they are in-themselves but rather that these objects as appearances conform to our way of representing, then the contradiction disappears; and consequently that the unconditioned must not be present in things insofar as as we are acquainted with them (insofar as they are given to us), but rather in things insofar as we are not acquainted with them, as things themselves in themselves (Sachen an sich selbst): then this would show that what we initially assumed only as an experiment is well grounded.* (CPR Bxviii-xxi, boldfacing in the original)

* This experiment of pure reason has much in common with what the chemists sometimes the experiment of reduction, or more generally the synthetic procedure. The analysis of the metaphysician separated pure a priori knowledge into two very heterogeneous elements, namely those of the things as appearances and the things in themselves. The dialectic once again combines them, in unison with the necessary rational idea of the unconditioned, and finds that the unison will never come about except through that distinction, which is therefore the true one. (CPR B xxi n., boldfacing in the original)

Now after speculative reason has been denied all advance in this field of the supersensible, what still remains for us is to try whether there are not data in reason’s practical data for determining that transcendent rational concept of the unconditioned, in such a way as to reach beyond the limits of all possible experience, in accordance with the wishes of metaphysics, cognitions a priori that are possible, but only from a practical standpoint. By such procedures speculative reason has at least made room for such an extension, even if it had to leave it empty; and we remain at liberty, indeed we are called upon by reason to fill it if we can through practical data of reason.* (CPR Bxxi-xxii)

* In the same way, the central laws of the motion of the heavenly bodies established with certainty what Copernicus assumed at the beginning only as a hypothesis, and at the same time they proved the invisible force (of Newtonian attraction) that binds the universe, which would have remained forever undiscovered if Copernicus had not ventured, in a manner contradictory to the senses yet true, to seek for the observed movements not in the objects of the heavens but in their observer. In this Preface I propose the transformation in our way of thought presented in the Critique merely as a hypothesis, analogous to that other hypothesis, only in order to draw our notice to the first attempts at such a transformation, which are always hypothetical, even thought in the treatise itself it will be proved not hypothetically but rather apodictically from the constitution of our representations of space and time and from the elementary concepts of the understanding. (CPR Bxii n.)

In my comments on Bxii-xiv, I spelled out the general form of Kantian abduction, aka Kantian inference-to-the-best-explanation, as a characteristic mode of natural scientific reasoning first discovered by Kant.

And in my remarks on Bxvi-xvii, I spelled out, in an anticipatory way, the fundamental analogy and necessary connection between Kantian abduction in natural science/physics, and Kantian abduction in philosophy, via transcendental deduction and transcendental proof.

But now Kant makes it fully explicit that transcendental deductions in particular and transcendental proofs in general just are Kantian abductions, aka Kantian inferences-to-the-best-explanation, and thus share essentially the same general form as Kantian abductions in natural science or physics.

The only basic difference, as I spelled it out in my discussion of Bxvi-xvii, is that whereas a Kantian abduction in natural science/physics is focused primarily on the synthetic a priori subjunctive conditional Γ[X1, X2, X3, … NCL, … Xn]□→ Y, and how the hypothetical antecedent general conception or theory Γ, including the general empirical natural causal law proposition NCL, explains the empirical factual consequent proposition Y against a transcendental backdrop, by contrast, a Kantian abduction in philosophy is focused on what metaphysically grounds that synthetic a priori subjunctive conditional Γ[X1, X2, X3, … NCL, … Xn]□→ Y considered as a whole — namely, the schematized Principles of Pure Understanding, the pure forms of human intuition, the original synthetic unity of apperception, and transcendental idealism — and then concludes by Kantian inference-to-the-best-explanation that this transcendental explanation or “transcendental proof” is a true philosophical explanation.

Hence,

[i]n this Preface I propose the transformation in our way of thought presented in the Critique merely as a hypothesis, analogous to that other hypothesis [put forward by Copernicus], only in order to draw our notice to the first attempts at such a transformation, which are always hypothetical, even thought in the treatise itself it will be proved not hypothetically but rather apodictically from the constitution of our representations of space and time and from the elementary concepts of the understanding. (CPR Bxii n.)

The other basic theme in the texts under III concerns Kant’s deeply controversial distinction between appearances/phenomena and things-in-themselves/noumena, which is later discussed in much detail in chapter 3 of the Analytic of Principles, “On the Ground of the Distinction of All Objects in General into Phenomena and Noumena” (CPR A235–260/B294–315).

Importantly, however, in the B Preface this distinction is also framed in terms of a fundamental analogy and necessary connection between Kantian abduction in natural science or physics, and Kantian abduction in philosophy.

But here the analogical emphasis is on the notion of an experiment and in particular on the notion of a “decisive test “ or Gegenprobe.

A leading theoretical virtue of a good scientific theory is that, via experiments, it isolates distinct elements in material or physical nature that are otherwise naturally combined into complex facts or mixtures, and may easily be misunderstood and falsely taken to be different from, or the same as, things that are, respectively and in reality, essentially the same or different.

For example, clouds may easily seem to be something other than water, lightning may easily seem to be something other than electricity, fool’s gold (i.e., iron pyrites) may easily seem to be the same as real gold (namely, Au, the element with atomic number 79) and hydrochloric acid (namely, HCL) or sulfuric acid (namely, H2SO4) might easily (and catastrophically) seem to be the same as water (namely, H2O):

Johnny was a chemist’s son, but now he is no more. For what he thought was H2O, was H2SO4.[i]

So too, a leading theoretical virtue of a good philosophical theory is that it solves philosophical puzzles, or paradoxes.

Kant’s claim is that transcendental idealism’s seminal distinction between appearances/phenomena and things-in-themselves/noumena, and the corresponding cognitive idealist thesis that all the proper objects of human cognition are appearances/ phenomena and never things-in-themselves/noumena is a decisive test or Gegenprobe of the truth of transcendental idealism, precisely because it prevents philosophical confusion and antinomy or hyper-contradiction — the “unavoidable conflict of reason with itself” (CPR Bxix n.) — in classical metaphysics’s and especially classical Rationalist metaphysics’ natural propensity to engage in transcendent impredicative reasoning.

But what precisely is transcendental idealism’s seminal distinction between appearances/phenomena and things-in-themselves/noumena?

This is, without a doubt, the most controversial, difficult, and written-about issue about the first Critique, not only because resolving it is essential for understanding the nature of transcendental and for critically evaluating its philosophical truth or falsity, but also because, sadly, Kant himself never fully resolved it, and more or less systematically oscillated between at least three different versions of the distinction:

(i) The Two Object or Two World Theory, which is a specifically Kantian version of substance dualism,

(ii) The Two Aspect or Two Standpoint Theory, which is a specifically Kantian version of ontological monism, namely, a One World Theory, together with an epistemic dualism, and

(iii) The Two Concept or Two Property Theory, which is also a specifically Kantian version of ontological monism or One World theory, together with a property-dualism-without-substance-dualism.[ii]

One thing we do know is that appearances or phenomena, are manifestly real natural objects such that

(i) asymmetrically necessarily, they conform to the non-empirical structures of our innate cognitive faculties, hence necessarily, they are related to human minds, and in at least that sense they are mind-dependent,

(ii) necessarily, they either are or can be directly present to human intuition and sensibility, and also fall under human concepts and understanding, hence necessarily, they are sensory and have sensory properties,

(iii) necessarily, they are spatiotemporal,

(iv) necessarily, they are causally empowered under natural causal laws, and

(v) necessarily, their existence and specific character is conditioned by causes that spatially exist earlier in time.

And, since things-in-themselves or noumena are, by hypothesis, essentially distinct from appearances or phenomena, it follows that, if they really exist, then they are non-manifest, non-natural objects such that

(i*) necessarily, they do not conform to the non-empirical stuctures of our innate cognitive faculties, hence necessarily, they are not related to human minds, and in at least that sense they are mind-independent,

(ii*) necessarily, they either are not or cannot be directly present to human intuition and sensibility, and also fall under human concepts and understanding, hence necessarily, they are non-sensory and have non-sensory properties,

(iii*) necessarily, they are non-spatiotemporal,

(iv*) necessarily, they are not causally empowered under natural causal laws, and

(v*) necessarily, their existence and specific character is unconditioned by any causes that spatially exist earlier in time.

Nevertheless, these five features occur explicitly under a conditional existential supposition, and we therefore need to know whether, according to Kant, things-in-themselves really do exist or not.

Let’s call this The Real Existence Question.

And here’s what Kant tells us in the B Preface about The Real Existence Question:

Our rational cognition a priori … reaches appearances only, leaving the thing itself in itself (Sache an sich selbst) as real (wirklich) for itself, but uncognized by us. (CPR Bxx)

Unfortunately, this formulation is at least four ways ambiguous and doesn’t tell us whether Kant is saying

(i) that things-in-themselves do really exist but are uncognized by us, or

(ii) that things-in-themselves do really exist but are uncognizable by us, or

(iii) that things-in-themselves possibly really exist but cannot be known either really to exist or not exist precisely because they are uncognized by us, or

(iv) that things-in-themselves possibly really exist but cannot be known either really to exist or not exist precisely because they are uncognizable by us.

Only formulation (iv) adequately captures the cognitive attitude of radical agnosticism about things-in-themselves/noumena that I spelled out in my discussion of the A Preface.[iii]

And as we shall see later, formulations (i) to (iii) each have apparently insuperable philosophical problems associated with them.

But at this point, Kant has not decisively plumped for any one of them.

Finally, the other thing that Kant tells us about appearances/phenomena and things-in-themselves/noumena here in the B Preface is that

[T]he same objects can be considered from two different sides, on the one side as objects of the senses and the understanding for experience, and on the other side as objects that are merely thought at most for isolated reason striving beyond the limits of experience. If we now find that there is agreement with the principle of pure reason when things are considered from this twofold standpoint, but that an unavoidable conflict of pure reason with itself arises with a single standpoint, then the experiment decides for the correctness of that distinction. (CPR Bxviii-Bxix n., boldfacing in the original)

This is a classic statement of The Two Aspect or Two Standpoint Theory of the appearances/phenomena vs. things-in-themselves/noumena distinction.

It’s also a classic statement of the One World or ontologically monistic interpretation of the appearances/phenomena vs. things-in-themselves/noumena distinction.

Again sadly, however, it’s at least three ways ambiguous, since it doesn’t tell us whether Kant is saying

(i) that there is one and only one class of apparent or phenomenal objects (that is, one apparent or phenomenal world, hence phenomenal monism) such that each member of this class can be considered phenomenally or noumenally by us, or

(ii) that there is one and only one class of things-in-themselves or noumenal objects (that is, one in-itself or noumenal world, hence noumenal monism) such that each member of this class can be considered phenomenally or noumenally by us, or

(iii) that there is one and only one class of non-phenomenal, non-noumenal objects (one non-phenomenal, non-noumenal world, hence neutral monism) such that each member of this class can be considered phenomenally or noumenally by us.

Even granting the fourfold ambiguity of what Kant has said here about The Real Existence Question, given what he has said about it, then it seems extremely unlikely that formulation (iii) captures the correct interpretation of The Two Aspect or Two Standpoint Theory.

For in that connection, nothing whatsoever has been said by Kant about any third or neutral class of objects apart from the class of appearances or phenomena and the class of things-in-themselves or noumena.

Nevertheless, again granting that fourfold ambiguity, unfortunately, formulation (i) and formulation (ii) are both consistent with what Kant has said here about The Real Existence Question.

Hence either of them, so far, could be a correct interpretation of The Two Aspect or Two Standpoint Theory.

It must also be frankly noted that there is also the very real critical question of whether the The Two Aspect or Two Standpoint Theory is philosophically acceptable under any reasonable interpretation of it.

I won’t, in this current connection, offer a definite answer to that question, although later in the commentary I will raise some serious doubts about that theory, and ultimately reject it.

But, just for the record, it must be noted here that the One World or monistic interpretation of the appearances/phenomena vs. things-in-themselves/noumena distinction is itself logically independent of The Two Aspect or Two Standpoint Theory.

For it’s perfectly consistent to hold, as a version of the One World or monistic interpretation, that

(i1) there’s one and only one class of apparent or phenomenal objects (that is, one apparent or phenomenal world, hence phenomenal monism), and

(i2) each member of the one and only class of apparent or phenomenal objects can be considered phenomenally by us, but

(i3) it makes no rational sense to consider apparent or phenomenal objects as in-themselves or noumenally, given the ontologically disjoint character of the classes of appearances/phenomena and things-in-themselves/noumena, hence no member of the one and only class of phenomenal objects can ever be intelligibly considered noumenally by us, but

(i4) at the same time, we can consistently think about, although never cognize and never know, things-in-themselves or noumena.[iv]

In this way one, can consistently deny The Two Aspect or Two Standpoint Theory and also accept a phenomenally monistic version of the One World interpretation of the appearances/phenomena vs. things-in-themselves/noumena distinction.

It should also be noted that (i1) through (i4) are all smoothly consistent with formulation (iv) of what Kant has said here about The Real Existence Question, which in turn adequately captures the cognitive attitude of radical agnosticism towards things-in-themselves/noumena.

So even leaving aside the question of whether, in 1781 or in 1787, Kant himself holds (i1) through (i4) as his all-things-considered version of the One World interpretation of the appearances/phenomena vs. things-in-themselves/noumena distinction, together with formulation (iv)’s version of an answer to The Real Existence Question, together with radical agnosticism about things-in-themselves/noumena, we could still not-implausibly assert that Kant rationally ought to have have held all these views, and also that their conjunction constitutes a philosophically defensible and recognizably Kantian, or at least broadly Kantian, philosophical theory.

The last important theme of the texts under III concerns the relationship between the metaphysics of the appearances/phenomena vs. things-in-themselves/noumena distinction on the one hand, and Kant’s practical philosophy on the other hand.

Just above, I critically analyzed Kant’s formulation of the distinction in terms of The Two Aspect or Two Standpoint Theory.

And in that context I listed five individually necessary and jointly sufficient conditions for something X’s being a thing-in-itself/noumenon:

(i*) X is mind-independent,

(ii*) X is non-sensory,

(iii*) X is non-spatiotemporal,

(iv*) X is not causally empowered under natural causal laws, and

(v*) X’s existence and specific character are not conditioned by any causes that spatially exist earlier in time.

Now, when we focus on (iv*) and (v*) together, we realize that, given these five criteria of thing-in-itselfhood/noumena-hood, it’s at least possible for things-in-themselves/ noumena to be causally empowered, provided that these noumenal causal powers do not fall under natural causal laws and also that the things-in-themselves/noumena are spatiotemporally unconditioned causes.

In other words, if things-in-themselves/noumena do have causal powers, then these powers are not naturally determined.

On the contrary, things-in-themselves/noumena are, or at least can be, absolutely spontaneous and self-determining causes.

This in turn closely relates to a certain theoretical pressure that apparently pushes Kant, in at least some passages in the B Preface, towards drawing the distinction between appearances/phenomena and things-in-themselves/noumena so sharply that it entails The Two Object or Two World Theory, together with ontological dualism.

Thus he says in the footnote at Bxxi and the corresponding main text following the note:

The analysis of the metaphysician separated pure a priori knowledge into two very heterogeneous elements, namely those of the things as appearances and the things in themselves. The dialectic once again combines them, in unison with the necessary rational idea of the unconditioned, and finds that the unison will never come about except through that distinction, which is therefore the true one. (CPR B xxi n., boldfacing in the original)

In other words, what Kant seems to be saying here is that although the distinction between appearances/phenomena and things-in-themselves/noumena as it’s construed according to The Two Aspect or Two Standpoint Theory, is sufficient for the purposes of theoretical reason and its scientific metaphysics, nevertheless, for the purposes of practical reason and its metaphysics of morals, only The Two Object or Two World Theory will suffice.

For only an ontological dualism can entail that ontically independent substances, which are also absolutely spontaneous and self-determining noumenal causes — so in effect, not merely things-in-themselves/noumena, but also free agents-in-themselves/noumena who are equally free persons-in-themselves/noumena — are possible.

But how can Kant consistently hold both of these claims?

One way around the apparent inconsistency would be for Kant to hold, on the one hand, that for the purposes of scientific metaphysics, we must be radically agnostic about the existence and nature of things-in-themselves or noumena, but also hold on the other hand, that for the purposes of the metaphysics of morals, we must have a specifically moral/practical belief or “faith”(Glaube) in our noumenal free agency and personhood (according to The Two Object or Two World Theory), even though, at the same time, it’s impossible for us to have specifically theoretical cognition (Erkenntnis) or scientific knowledge (Wissen) about these (according to either The Two Aspect or Two Standpoint Theory or The One World and Two Concept or Two Property Theory).

This Kantian two-step strategy, in turn, would require a careful distinction between moral/practical “belief-in” and scientific/theoretical “belief-about.”

I’ll come back to these important points in my remarks on Bxxx.

NOTES

[i] This gory but also amusing little rhyme — an effective mnemonic for simple Periodic Table-style chemistry — was taught to me as a child by my father, exists in multiple versions, and is of uncertain origin.

[ii] See R. Hanna, Kant, Science, and Human Nature (Oxford: Oxford Univ. Press, 2006), pp. 195–196 and 425–427. The Two Concept or Two Property Theory also holds that although things-in-themselves are logically possible, nevertheless precisely because we cannot cognize them, then we also know a priori that we cannot know whether they really do exist or do not exist, and therefore for the constructive purposes of real metaphysics, we can completely ignore things-in-themselves. Or in other words, it postulates methodological eliminativism about things-in-themselves.

[iii] Formulation (iv) is also a thesis of The Two Concept or Two Property Theory.

[iv] These four theses also all belong to The Two Concept or Two Property Theory.

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