1

Kant introduces the idea of a common sense in the Fourth Moment of his exposition of judgements of beauty. In §20, he first claims that judgements of beauty can be made only under the presupposition of a common sense. Next, he appears to answer in the affirmative the question that makes up the title of §21: ‘Whether one has good reason to presuppose a common sense’. Setting aside the details for now, we can sketch his argument as follows:

1. 1. Cognition requires that the cognitive faculties (i.e. the imagination and the understanding) be brought into the optimal ‘proportion (Proportion)’ or ‘inner relationship (innere Verhältniß)’.Footnote ³

2. 2. The optimal proportion of the cognitive faculties cannot be determined through concepts.

3. 3. So, the optimal proportion of the cognitive faculties must be determined through feeling.

4. 4. If the optimal proportion of the cognitive faculties and the feeling accompanying it were merely private, then cognitions would be merely private.

5. 5. Cognitions are not merely private, i.e. they are universally communicable.

6. 6. So, the optimal proportion of the cognitive faculties and the feeling accompanying it are universally communicable.

7. 7. A universally communicable feeling presupposes a shared capacity to sense it.

8. 8. So, there is good reason to presuppose a common sense.

I postpone further discussion of this argument until I present my own reading of common sense. First, I want to consider a question concerning the aim of §21 that has divided interpreters: does Kant intend the Optimal Proportion Argument to be a ‘deduction’ of judgements of beauty? That is, is Kant’s claim that the optimal relationship of the faculties is determined through a universally communicable feeling in cognition meant to play a role in justifying the claim to universal validity made by judgements of beauty? Given the question in the title of §21, as well as the broad similarity between Kant’s answer and the argument of the official deduction in §38, many interpreters believe that the Optimal Proportion Argument is a first attempt at a deduction.Footnote ⁴ A problem for this view, however, is that Kant concludes the very next section, §22, as follows:

Here, Kant indicates that he does not take himself to have investigated, much less settled, two related questions: whether there is a common sense, and whether the normative claim on the feelings of others that is made by a judgement of taste (i.e. beauty) is justified in itself or only expresses an independent interest in the possibility of intersubjective agreement. This suggests that Kant does not take §21 to contain a deduction of judgements of beauty that appeals to the role played by common sense in cognition. For if he did, how could he continue to regard these questions as unresolved in §22?

This is a primary reason that some interpreters deny that the Optimal Proportion Argument is a deduction of judgements of beauty and, indeed, that it is even concerned with such judgements. According to Allison and Matherne, for example, the common sense discussed in §21 is not the one said to be presupposed by judgements of beauty in §20, but a distinct species of common sense that Kant believes is required for cognition.Footnote ⁵ Kant brings up this ‘epistemic common sense’, on this reading, because its existence provides indirect support for the presupposition that there is also an ‘aesthetic common sense’, although it does not directly confirm it. And this is said to be why Kant continues to take the question about aesthetic common sense to be unresolved in §22, since he does not provide direct proof that there is an aesthetic common sense until the official deduction in §§38–40.

However, the suggestion that Kant posits two distinct species of common sense across §§20–2 strikes me as implausible for a few reasons. First, both §20 and §22 are explicitly about the role common sense plays in judgements of beauty, and so this interpretation must read Kant as switching to an entirely different common sense in §21 and back again in §22, without giving any indication that he is doing so. Second, the claim that the discussion of the conditions of cognition in §21 is not directly related to judgements of beauty ignores the many occasions – including in the official deduction itself (5: 290) – on which Kant explicitly identifies the conditions of making judgements of beauty with the conditions of cognition in general.Footnote ⁶ Here is just one example:

In this passage, Kant says that the ‘proportion’ of the cognitive faculties that is required for judgements of beauty is also required for cognition in general. This strongly suggests that he does not intend his discussion of the optimal ‘proportion’ in §21 to be limited to cognitive judgements, but to describe what is required for both judgements of beauty and cognition.Footnote ⁸

Third, a closer look at the question Kant says is left open in §22 undercuts the very motivation for distinguishing two species of common sense:

Two points are relevant here. First, recall that one of the main reasons to introduce a distinctively epistemic common sense is to explain how Kant can continue to claim in the above passage that the question of whether there is an aesthetic common sense is unresolved. But the question that Kant says is left open is not whether there is an aesthetic common sense in particular, but whether there is a common sense that is constitutive of the possibility of experience – in other words, precisely what would be considered the epistemic common sense. But this then rules out the suggestion for reconciling §§21–2, according to which Kant confirms the existence of an epistemic common sense in order to provide indirect support for an aesthetic common sense. Second, the passage clearly identifies the common sense that is ‘presupposed by us’ when we make judgements of taste as itself ‘a constitutive principle of the possibility of experience’. As I see it, this tells decisively against the proposal that there are distinct aesthetic and epistemic species of common sense discussed in these sections.Footnote ⁹

If there is only one species of common sense under discussion across §§20–2, however, we are again faced with the question of why Kant claims in quick succession both that there is good reason to presuppose a common sense and that he has not yet investigated whether there is one. We can resolve this puzzle, in my view, by attending to the difference between the goals of the Analytic of the Beautiful and the Deduction in §38. In the Analytic, Kant seeks to provide an ‘exposition’ (5: 279) of judgements of beauty – that is, a description of what is claimed by particular subjects that make such judgements. In the Deduction, in contrast, Kant considers whether subjects are justified in these claims. Now, Kant’s discussion in §§20–2 occurs in the Fourth Moment, within the Analytic of the Beautiful. And he makes clear that his point there is simply that particular subjects in fact presuppose a common sense when they make judgements of beauty. As he puts it, a common sense ‘is really presupposed by us: our presumption in making judgments of taste proves that’ (5: 239–40). Whether subjects are justified in this presupposition, he continues, will not be investigated in the midst of his exposition: ‘for now’, he says, ‘we have only to resolve the faculty of taste into its elements’ (5: 240).

The puzzle, of course, is how §21 – with its title question, ‘whether there is reason to suppose a common sense’ – fits into the expository goals of the Analytic. Since the question appears to be whether the presupposition of a common sense is justified, many interpreters take §21 to contain a first attempt – albeit a poorly located one – at a deduction. I think this is incorrect. We can distinguish two questions: first, whether particular subjects who make judgements of beauty have available to them, from their point of view, any grounds for believing in something like a common sense; second, whether there are philosophical and, indeed, transcendental grounds for doing so. As I see it, it is the former question that Kant asks in §21 and the latter that he puts off until the Deduction.Footnote ¹⁰

To further support this reading, note that the former question arises quite naturally at the point that Kant raises it. He has just explained that subjects who make judgements of beauty expect everyone to feel the pleasure they do, and that they make this surprising demand on others’ feelings by presupposing a common sense. Here it seems reasonable to ask why subjects would presuppose this: do they have any reasons available to them for doing so? In response, Kant answers that they do, since it seems to them that they also rely on something like a common sense in cognition. I put off the question of why this is the case until section 3. For now, I wish to argue only that Kant’s claim that particular subjects may take themselves to have reason to suppose a common sense is compatible with his denial that he has himself philosophically resolved the matter.

On my view, then, it is one and the same common sense that is presupposed by judgements of beauty and related to the conditions on cognition; Kant introduces it as part of his exposition of judgements of beauty in the Analytic, and goes on to confirm its existence in §40. Next, I present my interpretation of what this common sense amounts to.

2

To begin to understand what Kant means by common sense, it will be helpful to recall the conditions under which judgements of beauty are made. According to Kant, a judgement of beauty and the corresponding pleasure in the beautiful are grounded in the harmonious free play of the cognitive faculties of imagination and understanding. The harmony of the faculties also obtains in the case of cognition, since on Kant’s view cognition requires that the imagination synthesize the manifold of intuition in accord with concepts of the understanding. Thus, both faculties must harmoniously cooperate to generate a cognition with both intuitive and conceptual content. In the case of beauty, however, the harmony obtains while the faculties are in free play: although the imagination is ‘productive and self-active’ (5: 240), its synthesis is nevertheless found to be in accord with the understanding; as Kant puts it, ‘the former in its freedom is in harmony with the latter in its lawfulness’ (5: 287). This occurrence of harmony while the faculties are in free play results in a feeling of pleasure that is judged to be universally valid.

Now, despite their other differences, interpreters assume that the ‘sense’ in Kant’s common sense refers to the feeling of pleasure in the harmony of the faculties.Footnote ¹¹ In other words, they tie common sense essentially to the feeling of pleasure in the beautiful. On my view, there are a number of reasons not to do so. First, this identification is difficult to square with the role common sense actually plays in judgements of beauty: Kant describes it in §20 as a ‘principle … which determines only through feeling and not through concepts, but yet with universal validity, what pleases or displeases’ (5: 238, my emphases).Footnote ¹² Note that common sense is said to determine ‘through feeling … what pleases’ (I set aside the case of displeasure). If we identify the former feeling with pleasure, however, this sentence becomes difficult to interpret: it amounts to the seemingly trivial claim that common sense determines through pleasure what pleases.Footnote ¹³ Moreover, Kant’s phrasing here is not accidental. In §40, in which he describes taste itself as a common sense, he defines it as ‘the faculty for judging a priori the communicability of the feelings that are combined with a given representation (without the mediation of a concept)’. Here too, then, common sense is tied not directly to pleasure itself, but to a capacity that enables us to judge – without appeal to concepts, and thus through feeling (5: 239) – whether the pleasure that accompanies a representation is universally communicable. This suggests – as I will argue below – that what is directly sensed by common sense is not the feeling of pleasure, but rather another feeling that grounds the claim to the universal validity of pleasure.

A second reason to resist tying common sense to pleasure is that, as we have seen, Kant claims that the optimal ‘proportion’ or harmony of the faculties sensed by common sense obtains not only in judgements of beauty, but in cognition in general (5: 292–3).Footnote ¹⁴ But if this harmony were sensed through pleasure, this would entail that all cognition is pleasurable, a seemingly implausible thesis that most interpreters agree Kant is not committed to.Footnote ¹⁵

Third, Kant argues both that the feeling sensed through common sense is the ground of judgements of beauty, and that pleasure cannot be the ground of a judgement of beauty. The following passage states the former point clearly:

In contrast, as has been well-discussed, Kant raises a question in §9 that he claims is ‘key to the critique of taste’ – namely, ‘whether in the judgment of taste the feeling of pleasure precedes the judging of the object or the latter precedes the former’ (5: 216) – and argues there that pleasure cannot be the ground of a judgement of beauty, but rather must be its consequence (5: 217). As for the ‘determining ground of the judgment’ of beauty, he identifies it as the ‘feeling of the free play of the powers of representation … for a cognition in general’. Thus, Kant maintains both that (i) the ground of a judgement of beauty is a common feeling of the relation between the cognitive faculties; and (ii) the feeling of pleasure is not the ground but a consequence of a judgement of beauty. If we take these passages at face value, it follows straightforwardly that the feeling sensed through common sense is not identical to pleasure.Footnote ¹⁶

Admittedly, Kant does appear to link common sense to pleasure on one occasion. While rejecting the colloquial description of certain intellectual judgements as ‘common sense’, Kant points out that concepts like truth or justice utilized by such judgements cannot be expressed through a sense (5: 293). Instead, he notes that ‘if one would use the word “sense” of an effect of mere reflection’, it is aesthetic judgements that are better referred to as common sense, since ‘there one means by “sense” the feeling of pleasure’ (5: 295). As the arguments above demonstrate, however, the bulk of Kant’s text resists the identification of common sense with pleasure. Thus, I suggest we read the above sentence as making the narrower point that the colloquial tendency to describe certain judgements as common-sense judgements is better applied to aesthetic judgements than intellectual judgements, since only the former are expressed through a sensation – namely, pleasure.

To recapitulate, although Kant clearly connects common sense to a feeling, there are a number of reasons to conclude that this feeling is not identical to pleasure. First, the feeling in question is itself meant to play the role of determining what pleases or displeases; second, the feeling and the state it accompanies are said to be conditions on cognition in general, and cognition in general is not pleasurable; third, the feeling is said to be the ground of judgements of beauty, and Kant insists that pleasure is not the ground of judgements of beauty but rather its consequence.

In fact, there is direct textual evidence that two distinct feelings play an essential role in Kant’s account of judgements of beauty: the first, a sui generis feeling of the harmony of the faculties that is not itself pleasurable; the second, the feeling of pleasure itself. The following passage clearly distinguishes the two:

Here, Kant makes clear that the determining ground of judgements of beauty is the sensation of the harmonious play of the faculties, and twice repeats that the feeling of pleasure is not identical to this sensation but connected or combined with it. And the same distinction is repeated elsewhere.Footnote ¹⁷

On the basis of this textual evidence, as well as the above considerations concerning the role played by common sense, I argue that judgements of beauty have the following structure on Kant’s account. Their ground is a sui generis sensation or feelingFootnote ¹⁸ of the relation between the cognitive faculties as they represent the beautiful object. Through this sensation, the subject becomes aware of the relation of her faculties and judges that they are in harmony, as is required for cognition in general. The result is a feeling of pleasure which – since it is based in a state that is a universally valid condition on cognition – is itself universally valid.Footnote ¹⁹ This structure is clearly reflected, for example, in the following passage:

I have offered a full defence of this interpretation elsewhere.Footnote ²⁰ Here, I want to argue that these passages support a reading of common sense that illuminates the role it plays not only in judgements of beauty but in cognition in general. So far, I have denied that what is sensed through common sense is the feeling of pleasure. I am now in a position to offer a positive characterization: what is given through common sense, I argue, is the sui generis sensation of the relationship between one’s cognitive faculties, and in particular, in the case of beauty, the sensation of the harmony of one’s faculties which is the ground of judgements of beauty.

We can now explain why Kant says in §§20–23 that anyone who makes a judgement of beauty presupposes the existence of a common sense. Recall that on Kant’s view, a subject who judges an object to be beautiful claims that everyone ought to feel the pleasure in it that she does. As we have seen, her pleasure is based in the feeling of the harmony of her faculties. Now, in order to claim that everyone ought to share her pleasure, she must assume that the feeling of harmony in which she takes pleasure is not merely private but is available to all. She must assume, that is, that anyone can sense the harmony of their faculties in the same circumstances. As an analogy: if I claim you ought to share the pleasure I feel in a particular wine, I have to assume you can taste the wine and it tastes the same to you as it does to me.Footnote ²¹ Similarly, if I claim you ought to share the pleasure I feel in the state of mind a beautiful object puts me into, I have to assume you can sense your state of mind and it feels the same to you as it does to me. In short, as Kant puts it, I have to assume we share a common sense that allows us to sense the harmony of our cognitive faculties.

Moreover, we can see why, when Kant posits a common sense, he treats it as a substantive presupposition triggered in particular by judgements of beauty.Footnote ²² After all, if common sense were just the capacity to feel pleasure, the assumption that others share this capacity would arise not only for judgements of beauty, but also at least for judgements of the good, which Kant also believes are accompanied by a pleasure claimed to be universally valid (5: 213). On my account, in contrast, Kant’s goal is to introduce a novel sense, namely, a capacity to sense the relationship of our cognitive faculties as they engage in representation. Kant repeatedly emphasizes the surprising claim that this relationship can be sensed:

Let me consider an objection here. When Kant first introduces common sense as a condition of judgements of beauty in §20, he describes it as ‘the effect of the free play of our cognitive powers’ (5: 238, my emphasis). This appears to conflict with my claim that it is specifically the harmony of the faculties that is sensed through common sense. Moreover, since the cognitive faculties are not free in the case of cognition, it also makes it unclear how common sense so described could play any cognitive role.Footnote ²⁴ In response, I would note that Kant often uses ‘free play’ as shorthand for referring to the state the cognitive faculties are in in the case of beauty – which, as we know, is more fully described as a state of harmonious free play. A particularly relevant example of this is at 5: 218, where Kant refers to ‘the state of mind in the free play of the imagination and the understanding’ as a ‘subjective relation suited to cognition in general’, clarifying however that this is ‘so far as [these faculties] agree with each other as is requisite for cognition in general’ (my emphases). On my reading, it is this agreement or harmony of the faculties – which happens to obtain in free play in the case of beauty – that is suited to cognition in general.Footnote ²⁵ And this is correspondingly the strategy I suggest we adopt in reading §20 as well. Doing so is supported by the fact that Kant’s other discussions of common sense – both in the case of beauty and cognition – connect it explicitly to the feeling of an optimal relation between the faculties, rather than to their being free or in play.

3

Let us now return to §21 and the Optimal Proportion Argument, where, as we have seen, Kant appeals to the role common sense plays in cognition to argue that particular subjects have reason to presuppose a common sense. My goal in this section is to identify this role, and in so doing, defend my claim that common sense provides the essential link between beauty and cognition for Kant.

I have argued that common sense enables us to sense the harmony of the faculties, and that this harmony is a necessary condition both of judgements of beauty and cognitive judgements. The latter point suffices to explain Kant’s initial discussion of common sense in §21. He begins by claiming that cognitions must ‘be able to be universally communicated (allgemein mittheilen lassen)’, and continues:

Cognition, on Kant’s view, is essentially universally valid and universally communicable. When a subject makes a cognitive judgement about an object, he argues, she in effect claims that her judgement is universally valid: that is, that it does not express a merely private mental state that she happens to be in, but rather that any subject in her cognitive circumstances ought to make the same judgement.Footnote ²⁶ In doing so, she also in effect claims that her judgement is universally communicable: that is, that the necessary conditions for making the judgement are possible for any subject.Footnote ²⁷ Now, as we have seen, it is Kant’s view that the harmony of the faculties is a necessary condition on cognition in general. It follows that any cognitive subject must be able to have the harmony of the faculties. In Kant’s words, the ‘proportion’ of the faculties that is ‘suitable for making cognition out of a representation’ must itself be universally communicable.

But Kant does not stop with the claim that all cognitive subjects must be able to have the harmony of the faculties. Rather, as we saw in the Optimal Proportion Argument, he adds that every subject must be able to feel this harmony, and thus, that there must be a common sense:

The question, of course, is why exactly Kant claims all cognitive subjects must be able to feel the harmony of their faculties. One explanation, offered by Guyer, is that he is relying on a ‘same cause, same effect’ principle: if cognition requires that every subject have the harmony of the faculties, and this harmony causes a feeling, then we can predict that every cognitive subject feels the harmony.Footnote ²⁸ However, this explanation seems to rely on the very kind of ‘psychological observation’ Kant rules out as a basis for assuming a common sense, since it appeals to the fact that the harmony of the faculties happens to cause a feeling in subjects like us. In contrast, Kant argues in the passage above that we can know a priori that cognitive subjects must be able to feel the harmony of their faculties, since cognition depends on subjects being able to determine through feeling when their faculties are in the ‘optimal … disposition’ or harmony. It is for this reason that he concludes that common sense is a condition on the universal communicability of cognition itself.

But why should we think cognition depends on a feeling and so, requires a common sense? Here, some interpreters appeal to Kant’s claim in the Critique of Pure Reason that judging whether a particular falls under a concept requires a ‘special talent’ (A133/B172). According to Allison, for example, this suggests that judgers must have a capacity for ‘immediately seeing (without appeal to rules and therefore “feeling”) whether … a given intuited manifold accords with a particular concept’.Footnote ²⁹ On this view, it is this capacity to ‘feel’ whether a concept one possesses applies to a particular that calls for a common sense. However, it should be noted, first, that Kant never associates the talent in question with a feeling; and second, that he makes clear it is by no means common. In fact, he expressly allows that even a learned physician, judge or statesman might ‘stumble in their application’ of theoretical rules because they lack the talent for judgement (A134/B173). As I see it, this makes it a poor candidate for a shared common sense that is meant to be a condition on cognition as such.Footnote ³⁰

In order to understand the role the feeling of harmony plays in cognition, I argue we should look not to the Critique of Pure Reason, but to the Critique of Judgement itself, and in particular, to what could be considered its unifying topic – the type of judgement that Kant calls ‘reflecting (reflectirende)’ judgement. When a subject subsumes a given particular under a concept she already possesses, she makes a ‘determining (bestimmende)’ judgement; in contrast, when she subsumes a given particular under a new concept that she thereby acquires, she does so through a reflecting judgement (5: 179). As Kant notes in the introductions to the Critique of Judgement, although he did not discuss reflecting judgements in the first Critique, they are nevertheless essential for empirical cognition, since it is through them that we come to have the empirical concepts necessary for experience (20: 212–13; 5: 180–2). I will now argue that common sense plays a necessary role in these reflecting judgements through which we acquire empirical concepts, and it is this role Kant has in mind when he claims common sense is necessary for the universal communicability of cognition.Footnote ³¹

Reflecting judgements through which we acquire empirical concepts share an important feature with judgements of beauty (indeed, both are species of reflecting judgement). In both cases, the subject is presented with a particular for which she does not have an adequate concept and, as a result, the imagination synthesizes the manifold in a manner that is not determined to accord with the understanding. After this, the two cases diverge in important ways. In the case of beauty, the freely synthesized form of the object is itself felt to give rise to the harmony of the faculties, and the result is the distinctive pleasure in the beautiful. In the other case, in contrast, the subject compares the given representation with others she judges to fall into the same empirical class as it, a class for which she thereby acquires a concept. A well-known example of the latter is found in the Jäsche Logic, where Kant describes the process of acquiring the concept ‘tree’ by comparing representations of particular trees:

An obvious question about Kant’s example is what makes it the case that I select the spruce, willow and linden for comparison in the first place. The answer cannot be that I recognize they are all trees, or even that I recognize they are similar, because that recognition is only supposed to arise as a result of my comparison and, as such, cannot antecedently inform what I choose to compare.Footnote ³²

To respond to this question, I will draw in part on Ginsborg’s reading of Kant’s account of empirical concept acquisition, which appeals to the role played by the reproductive imagination (Ginsborg Reference Ginsborg2015: 159–62). For Kant, the reproductive imagination is the capacity to recall to mind representations previously had by a subject. It is governed by laws of association, which make it the case that representations that have often accompanied each other in the past come to mind together (A100). In his lectures on anthropology, Kant specifies the bases of association, namely ‘accompaniment, contiguity, and … relation … [of] similarity and derivation’. Successive or simultaneous events bear the relation of accompaniment, leading to the type of association in Kant’s example: ‘if we see smoke, then the representation of fire immediately appears’. Things at or near the same location bear the relation of contiguity: ‘if one thinks about the place where one enjoyed oneself, the people who were present there come to mind’. Things which ‘come from one basis’ bear the relation of derivation: ‘if it rains and the sun shines, one immediately looks around [to see] if there is not a rainbow’. Finally, things that belong ‘to certain classes’ bear the relation of similarity, such that ‘if we think of one thing, the other comes to mind’ (Lectures on Anthropology, 25: 512–13).

Now, one or another of these relations could very plausibly explain why a subject finds herself thinking together of a spruce, willow and linden. Perhaps these representations are associated because she encountered these trees in the same forest. Or perhaps their very similarity makes it the case that that seeing one automatically calls the others to mind. Either way, we can explain why these trees come to a subject’s mind by appealing to associations due to her reproductive imagination, without needing to attribute to her the antecedent capacity to recognize that they are all trees or even that they are similar in specific respects.

Indeed, there is evidence that Kant takes the imagination and its associations to play an important role in the acquisition of concepts. In his notes on logic, amidst an extended discussion of empirical concept formation, he says it is through the comparison of imaginatively combined representations that we clarify the concept that applies to them (Refl. 2878, 16: 556–7). In another note, he adds that we do so by ‘compar[ing] only what is common in the rule of our apprehension (Regel unserer Auffasung)’, and offers the following examples of the kind of rule he has in mind: ‘one sees a bush, so one can represent a tree; an elongated rectangle gives rise to a square’ (Refl. 2880, 16: 557). The similarity between these examples and the ones from Kant’s lectures above strongly suggests that what he means by a ‘rule of … apprehension’ here is a particular associative habit that exists for a subject. This would be in line with Kant’s claim in the first Critique that apprehension essentially involves reproduction (A102), as well as his description of associations as subjective rules (A100, A121).Footnote ³³ Thus, these passages support the claim that, on Kant’s view, we acquire empirical concepts through a comparison of what is common among representations that have been reproduced according to an associative rule.

In order to count as acquiring a new concept, however, it is not enough to have a set of representations come to mind and recognize similarities in their content. Rather, the similarities must be taken as a basis for judging that the represented objects belong to the same empirical class. For Ginsborg, this further step consists in the awareness that a particular association is ‘appropriate’ (Ginsborg Reference Ginsborg2015: 160), that is, that it expresses ‘how I (and everyone else) ought to associate representations’ (p. 163). She claims this awareness is ‘primitive’: there are no antecedent criteria associations are judged to satisfy in virtue of which they are appropriate (pp. 163–8).

One problem, however, is that most associations will not be regarded as appropriate, at least not in the relevant sense of presenting objects that belong to the same empirical class. We only need to look back at Kant’s own examples of associations to see this: fire with smoke, a sunny rainfall with a rainbow, etc. Thus, an important question that Ginsborg does not answer is why we only regard some associated representations – such as those of the spruce, willow and linden – as belonging to one empirical class and, in so doing, acquire a new concept.Footnote ³⁴ What distinguishes these representations from those we do not classify together?

The answer may at first seem obvious: unlike the other cases, comparing representations of the spruce, willow and linden reveals that they have a number of features in common. In general, we might respond, it is only if compared representations are sufficiently similar that we classify them together. However, it is hard to more precisely specify what it means for representations to be sufficiently similar in the relevant respect. For one, almost all objects will appear similar in some respects. Moreover, objects may appear similar in many respects without being judged to fall into the same class – consider, for example, a leafless tree and a wooden pole. Conversely, objects may be judged to fall into the same class despite having few apparent similarities – two chairs with very different forms and materials, say, or a leafless tree and a flowering bush. In short, it is not clear that there are determinate criteria that can be said to systematically guide the comparison of associated representations and distinguish those judged to form the basis of an empirical concept from those that are not.

Indeed, Kant argues that reflecting judgements by which we acquire empirical concepts ‘requir[e] a principle’ that governs them just as determining judgements do (20: 211). Whereas the latter are governed by the particular concept(s) one applies in them, Kant points out that, in the case of a reflecting judgement, ‘one cannot refer it … to already known empirical concepts’ (20: 213). Instead, he argues, reflecting judgements must be governed by an a priori principle, which he states as the principle that ‘for all things in nature empirically determinate concepts can be found’ (20: 211).Footnote ³⁵ As Kant understands it, this amounts to the assumption that, despite the ‘immeasurable multiplicity of things’ in nature, we can find ‘sufficient kinship among them’ to subsume them under a system of empirical concepts governed by empirical laws (20: 215). In short, Kant argues that reflecting judgements must assume that nature is ‘purposive’ for our faculty of judgement (20: 202–4; 5: 184), that is, that it is suitable to be judged by us.

Now, by itself, Kant’s principle of reflecting judgement appears much too general to offer a response to our question about why some associated representations form the basis of empirical concepts whereas others do not. Indeed, he describes it as an ‘indeterminate (unbestimmtes) principle’, one that cannot be ‘explain[ed]’ or ‘determine[d] … more precisely’ (20: 214). How, then, is this principle applied in particular reflecting judgements? Here is what Kant says:

In the First Introduction, Kant explains that he calls a proposition ‘technical’ if it ‘belong[s] to the art of bringing about that which one wishes should exist’ (20: 201). He adds:

Kant’s point in these passages is that reflecting judgements by which we acquire empirical concepts are not determined by objective criteria that we antecedently possess. Instead, they treat nature as if it were ‘technical’ or ‘artistic’ in relation to our faculty of judgement – that is, as if nature had designed its products and their relation to each other with a purpose in mind, namely, the purpose of being judgeable by beings with cognitive faculties like ours. Kant describes this as a subjectively necessary principle (20: 209): although we do not have objective grounds for its truth, it is necessarily presupposed by our empirical investigation into nature (5: 184).Footnote ³⁶

In our search for empirical concepts, then, we assume that nature is purposively designed in relation to us and set out, so to speak, to uncover that design. For Kant, as we have seen, acquiring new empirical concepts requires comparing representations that have been called to mind by the reproductive imagination. I have argued that a question we face in such cases is whether particular reproduced representations are sufficiently similar to count as presenting objects that belong to the same empirical class. Kant’s claim that the procedure we follow in acquiring empirical concepts is ‘technical’ suggests that this question should be understood in relation to our cognitive faculties as follows: does it seem as if these objects were designed in order to be graspable by us under one empirical concept? That is, does this set of representations that has been reproduced by the imagination conform with the general requirements of the understanding as a faculty for concepts?Footnote ³⁷

How can the question so restated be answered? Since the purpose of the assumed design is for objects in nature to be suitable to our cognitive faculties, I suggest we can discover instances of it by attending to the effect particular representations have on our cognitive faculties. Indeed, Kant makes clear that when we reflect for the sake of an empirical concept, we can have what he calls an ‘inner perception of a purposiveness of representations’ (20: 220, my emphasis):

What this ‘inner perception’ enables awareness of, he adds, is whether or not the imagination and the understanding are in harmony, as required for judgement in general (20: 220). If having a particular set of representations in mind puts our faculties into harmony, then since the harmony of faculties is a necessary condition for cognition, the represented objects will appear as if designed to be grasped together in one cognition by us.Footnote ³⁸ It is in such cases, I suggest, that we classify the objects together and acquire a new concept for them. On my view, this is why Kant claims that the same ‘procedure of the power of judgment’ is employed both ‘for the sake of an empirical objective concept’ and in ‘aesthetic judging’, namely a procedure that relies on sensing the harmony of the faculties (5: 292).

If this is right, we are finally in a position to understand Kant’s claim that common sense – which I have argued is the capacity to sense the relation of our faculties – is a necessary condition on cognition. Cognition requires the application of empirical concepts, and as we have just seen, the reflecting judgements by which we acquire empirical concepts depend on our ability to sense when our faculties are in harmony. This is the role for common sense I believe Kant has in mind when he claims in the Optimal Proportion Argument that cognition depends on our ability to determine the optimal relationship between our faculties ‘through the feeling (not by concepts)’ (5: 239).Footnote ³⁹

Additionally, it should be noted that a judgement that classifies a set of objects under an empirical concept essentially claims universal validity. When a subject classifies the spruce, linden and willow as trees, she does not claim that this is merely how she privately sorts them; rather, she effectively claims that it is correct to, and so that everyone ought to so classify them. But since, as we have seen, making this judgement partly depends on feeling the harmony of the faculties, this claim presupposes that everyone can feel the harmony in the same circumstances. This explains why Kant says specifically in the Optimal Proportion Argument that the universal communicability of cognition presupposes the existence of a common sense. If the capacity to feel the harmony of the faculties were not shared, judgements involving empirical concepts would not be universally communicable and could only claim private validity. Since cognition is essentially universally communicable, Kant concludes, there must be a common sense.

One last point is in order here. In section 1, I suggested that the question Kant is asking in §21 is whether particular subjects who make judgements of beauty have any reasons available to them for presupposing a common sense. As we have seen, he answers affirmatively, on the ground that common sense plays a necessary role in cognition. In this section, I have sketched this role by arguing that common sense is necessary for the reflecting judgements through which we classify objects. But does Kant really think this role is accessible to particular subjects? One indication he does is his claim that, although we may not ordinarily notice the purposiveness displayed by nature in ‘the unity of its division into genera and species, by means of which alone empirical concepts are possible’, this is only because ‘the most common experience would not be possible without it’ (5: 187). He adds that we can indeed become ‘attentive to’ this purposiveness and that doing so even gives rise to a feeling of pleasure in us (5: 188).Footnote ⁴⁰ What we can attend to, on my view, is the feeling of harmony that underlies judgements by which disparate objects are unified under a system of concepts. Since these judgements are essential for cognition, claim universal communicability and, as I have argued, are partly determined by the feeling of harmony, particular subjects indeed have good reason available to them to regard the capacity to feel the harmony of the faculties as a shared capacity. In short, they have good reason to presuppose a common sense.

Is the claim that a feeling of harmony plays a necessary role in the acquisition of empirical concepts plausible? I cannot offer a full interpretation and defence of Kant’s account of empirical concepts here, but let me offset a possible worry. In assigning this role to common sense, I do not intend to deny that other factors – such as the relevant scientific knowledge or our practical interests – play a crucial role in determining how we classify objects. My suggestion is that in most cases these factors will leave open several possibilities and, as such, will underdetermine the correct way to proceed. Kant’s claim, as I understand it, is that in such cases we must proceed in a way that feels cognitively right to us, even if we later revise this based on further information. As he puts it, the fact that ‘there is such a manifold of forms in nature’ means that in ‘ascending from the particular … to the universal’, the reflecting power of judgement must ‘regar[d] as necessary’ what ‘may seem to be contingent’ to our understanding (5: 179–80). The choice of one classificatory scheme over another can seem contingent because it is underdetermined by the available objective criteria. In the face of this indeterminacy, Kant argues, we determine how to proceed partly on the basis of subjective criteria having to do with our own cognitive faculties. We proceed, that is, on the assumption that nature has placed its joints where they are most comprehensible to us and best accord with our cognitive needs – including, importantly, the need that our faculties be in harmony.Footnote ⁴¹