1. Introduction
This paper argues that ‘heart’ (Herz) is a distinctive technical term for Kant which plays an important role in his mature moral psychology. Kant’s work may seem a surprising place to look for insights on matters of the heart. His ethics have frequently been criticised for their supposedly cold, formalistic outlook. Kant’s few references to the heart in his best-known ethical works, such as the Groundwork, only appear to reinforce this impression. For instance, he (in)famously characterises the actions of a person with ‘little sympathy in [his] heart’ (GMS, 4: 398), who nevertheless does good to others from duty alone, as an example of genuine moral worth.Footnote 1 It seems easy to conclude, then, that Kant thought little about the heart and set it aside as playing no real role in his ethics.
Religion within the Boundaries of Mere Reason presents a striking contrast to this picture, however. In this text, the heart occurs frequently and occupies a central, if often overlooked, philosophical role. Agents are morally categorised as having good or evil hearts (RGV, 6: 29, 30, 37, 57, 163). ‘Heart’ features in Kant’s terms for the decisive moment of moral reform (Herzensänderung, ‘change of heart’) (6: 47, 72, 76) and for God as a knower of our innermost moral convictions (Herzenskündiger, ‘knower of hearts’) (6: 48, 67, 72, 99, 189). Kant describes the invisible church or moral community as a ‘union of hearts’ (6: 102) and the true service of God as ‘service of the heart’ (6: 192). He frequently refers to the depths of the heart (6: 48, 63, 198; cf. MS, 6: 392, 441, 447) and to both the moral law and the rational religion based on it, as ‘inscribed’ upon the heart (RGV, 6: 104, 159, 181).
This contrast raises three interconnected questions which this paper will address. Firstly, what is the heart for Kant? Secondly, what explains its apparent shift from periphery to prominence in Religion? Thirdly, what is the significance of this shift and of the heart in Kant’s mature moral psychology?
At first glance, each appears to have a straightforward and relatively uninteresting answer. To the first question, Kant never defines ‘heart’ clearly in Religion or other published work, nor does he introduce it explicitly as a technical term. It is therefore easy to assume he is simply using a culturally familiar metaphor in its ordinary, vague meaning. To the second question, the metaphor of ‘heart’ is prominent in the language of Christianity, especially the German Pietist variety that Kant grew up in. It is thus no surprise that it occurs more frequently in a text about religion. To the third question, we then seem forced to conclude that the heart is of no philosophical significance. Call this set of answers the default view. While the default view is rarely made explicit, it likely plays a role in explaining why Kant’s concept of heart has garnered little attention and why interpreters who note Kant’s usage of it tend to reduce it to more familiar concepts like ‘character’ (Papish Reference Papish2018: 156n) or ‘will’ (Palmquist Reference Palmquist and Kant2009: xxv) or assume instead that it refers strictly to our subjective feelings (Herman Reference Herman and Herman2022: 199).Footnote 2
I will show that the default view is mistaken on all three questions. The heart is not only central to the philosophical project of Religion but also to the development of Kant’s thinking about moral agency generally. To see this, we have to look beyond the text of Religion, on which the few extant discussions of Kant’s notion of heart have focused almost entirely. In his earlier lectures on anthropology, Kant repeatedly offers and gradually develops explicit characterisations of ‘heart’ which have been virtually ignored in the literature.Footnote 3 These show that Kant took it seriously as a philosophical term of art. However, though these discussions of ‘heart’ occur in almost every set of lecture notes we have up until the 1780s, they disappear entirely from the corresponding sections of Kant’s 1798 published Anthropology based on these notes. In roughly the same period, the heart shows up instead in texts that deal with Kant’s ‘moral religion’: the 1793 Religion as well as the 1798 Conflict of the Faculties (SF, 7: 24, 55, 64, 74).Footnote 4 This suggests Kant made intentional decisions about his usage of the concept based on a changing understanding of its place in his system.
My developmental approach shows that Kant’s basic understanding of the heart remains consistent from the early lectures to Religion. ‘Heart’ consistently refers to the power of the faculty of desire to generate Triebfedern, or ‘incentives’, based on feelings.Footnote 5 These Triebfedern in turn cause desire and therefore action. However, the role and scope of this power change significantly in order for Kant’s theory of action to meet the demands of his developing moral theory. Initially, Kant locates the heart entirely within the agent’s characteristic Sinnesart (‘way of sensing’) or ‘natural’ temperament, contrasting with the Denkungsart, ‘way of thinking’, which is based on freely chosen principles. Because we are only morally responsible for what is up to us, Kant increasingly emphasises the latter over the former as his moral theory develops. In his most widely read ethical texts, he flirts with an ‘intellectualist’ view of desire, according to which at least some Triebfedern are grounded directly in moral judgements without the intervention of feeling, thus motivating action while bypassing the heart entirely. His considered view, however, is that all motivation requires feeling; in other words, all desire stems from the heart. Kant’s moral theory, nevertheless, demands that we be responsible for these desires and that they be not merely the result of our natural temperament. His radical solution in Religion is to reconceive the heart as encompassing both our empirical, natural temperament (Sinnesart) and our intelligible, freely chosen character (Denkungsart). Whether we have a good or evil heart is no longer a natural fact of our temperament but the result of a free choice. This choice partly determines the way in which we respond to our feelings and form desires. Kant’s concept of the heart thus moves from descriptive to moral-anthropological, which explains its conspicuous absence from his descriptive Anthropology.
This conclusion has significant upshots for Kant’s theory of agency. We are responsible not only for the principles we adopt but also for the feelings and motivations we have. Reason does not simply stand over these feelings, responding to them or trying to bring them under control. It is instead intimately connected to them within the heart, where its moral choices can transform those feelings and our reaction to them for good or for ill. Conversely, because the heart still reflects a characteristic temperament, it allows our commitments for or against the moral law to express themselves in ways that reflect our distinct personalities and affective histories. Far from being a matter of indifference to Kant, then, a rich view of the heart turns out to be central to his mature view of moral action.
In section 2, I examine Kant’s early account of the heart, focusing especially on its development in his anthropology lectures. In section 3, I show how Kant’s mature account of the heart in Religion connects intelligible and empirical characters. In section 4, I discuss systematic implications of this account. In section 5, I respond to two important objections it faces. Firstly, does it actually explain anything? Secondly, if the heart is so important, why does Kant not draw attention to it as such? In section 6, I conclude by answering the three questions posed above.
2. The heart in the early Kant
Occasional references to the heart occur throughout Kant’s published works. However, he always appears reluctant to define it there. For instance, while the term and its cognates (‘tenderheartedness’, ‘goodheartedness’, etc.) occur repeatedly in the 1764 On the Feeling of the Beautiful and the Sublime (BGSE, 2: 215–8), it is defined only in specific usages.Footnote 6 In his anthropology lectures, however, characterisations of the heart are a mainstay for Kant, occurring in nearly every set of student lecture notes we have. They display both a consistency over time and a gradual refining of the term’s place in Kant’s conceptual repertoire, which together make it indisputably clear that it is his own technical term.
Kant’s references to Herz mostly occur within a cluster of related terms which begin closely associated and then become increasingly differentiated over the years. Early on (1772–3), Kant equates the heart to Gemüth, usually translated as ‘mind’:Footnote 7
The mind [Gemüth] is otherwise called the heart, which therefore borders on the higher powers of the human mind. A good mind or heart is the good relation between sensations or inclinations, and the reaction of the understanding. (V-Anth/Collins, 25: 17)
Strikingly, Kant describes Gemüth/heart as relating two faculties, here those of feeling and understanding. In later lectures, Kant retains this view that both heart and Gemüth relate feeling to another basic faculty even as he begins to draw a clear distinction between them. His considered view of Gemüth remains close to that expressed above, whereas we will see that he comes to associate the heart with the faculty of desire insofar as it responds to feeling. The heart is active, while the Gemüth is merely passive.Footnote 8
A representative statement of the distinction in the Pillau notes (1777–8) bears this out:
If I say that someone has a good Gemüth, I understand by this a purely passive quality; a good heart, however, is an active quality. Both belong to temperament. A Gemüth is good, insofar as it holds within it no resistance to the good; but the heart is good insofar as it has a drive to the good within it, which is however sensible. … The good heart is then an instinct to do something good, but the good Gemüth is a susceptibility not to activity, but to being led by others. (V-Anth/Pillau, 25: 817; cf. V-Anth/Mrongovius, 25: 1369)
To have a good Gemüth is merely to be easily influenced by others. A good heart, by contrast, is oriented to good action. Kant’s claim that it is an instinct to do good does not recur in later lectures and is perhaps unhelpful. However, since he thinks of instinct as a ‘type of desiring’ (V-Anth/Busolt, 25: 1518; cf. V-Anth/Friedländer, 25: 583; Anth, 7: 265; Frierson Reference Frierson2014: 66), it tells us that Kant already associates the heart with the faculty of desire, which causes action (V-Anth/Busolt, 25: 1514; cf. KpV, 5: 9; MS, 6: 211).
Both heart and Gemüth fall under temperament, which refers to the natural propensities and drives of an agent. The late (1788/9) Busolt notes characterise temperament as follows:
Temperament is properly the characteristic of the power of life, insofar as it does not belong to the rationality of the human being. It is physical and psychological … The temperament of the soul is the proportion of the incentives [Triebfeder] … One can call the temperament the way of sensing [Sinnesart]. (V-Anth/Busolt, 25: 1531)
Temperament is characteristic, i.e., makes an individual the human being that they are. It does so in virtue of how their Triebfedern are proportioned to one another, where a Triebfeder is a ‘subjective ground of desire’ (GMS, 4: 42; cf. KpV, 5: 72). Temperament is natural and not rational, i.e., not self-chosen. Kant consistently equates temperament with Sinnesart (‘way of sensing’) (V-Anth/Pillau, 25: 821; V-Anth/Mrongovius, 25: 1368).
Temperament contrasts with character, which becomes increasingly prominent in Kant’s later lectures.Footnote 9 Character describes the principles to which one freely binds their will (V-Anth/Friedländer, 25: 628; cf. V-Anth/Pillau, 25: 822, Anth, 7: 292). As temperament is equated to Sinnesart, Kant regularly identifies character with Denkungsart, ‘way of thinking’ (V-Anth/Menschenkunde, 25: 1156, 1169; V-Anth/Mrongovius, 25: 1368, 1385, 1386; V-Anth/Busolt, 1530). Whereas ‘Gemüth and heart rest merely on feeling’, ‘[c]haracter rests properly on the authority of the understanding’ (V-Anth/Menschenkunde, 25: 1159). A passage in the 1781–2 Menschenkunde notes lays out their relationship clearly:
A good heart consists in the real activity of doing good, yet only according to a certain instinct; in this it is distinguished from character, which is the activity of doing good from principles. For the good mind [Gemüth], no Triebfedern are necessary, because it is merely passive; only in the good heart there is always an impulse, even if these are not true principles [wenn dies auch nicht wahre Grundsätze sind]. (25: 1158)
As Kant’s moral theory develops, he increasingly emphasises that only whatever is under the agent’s control can be a source of moral worth. It is, accordingly, no surprise that he gradually foregrounds character, while heart fades into the background.
The later notes bring a final contrast into view between heart and head (Kopf). In sections that deal primarily with the head, Kant also offers perspicuous contrasting characterisations of the heart.Footnote 10 For instance:
Of the head. The head means the sum of all talents which belong to the power of cognition. The heart by contrast consists in the sum of all Triebfedern which move the will, and which are the ground of all acting and refraining. (V-Anth/Menschenkunde, 25: 1051–2)
What is characteristic of human beings in the faculty of cognition is called the head; in the faculty of desire, the heart. (V-Anth/Mrongovius, 25: 1308)
These passages develop the claim that the heart is active and make explicit that it is a power of the faculty of desire. Human beings have the distinctive hearts they do based on the distinctive motivations they have. To ‘take something to heart’, not just ‘to mind [Gemüth]’ is to make it a Triebfeder to action (25: 1321).Footnote 11 The heart remains associated with sensibility (25: 1369): it is the power of the faculty of desire that takes sensible feelings as input and produces Triebfedern as output.
Heart is the counterpart of ‘head’ insofar as both are characteristic of a human being with respect to a faculty. We can understand this notion of ‘characteristic’ as what is not captured at the level of analysis of Kant’s Critiques. The first two Critiques describe how the faculties of cognition and desire must operate for cognition and moral action to be possible without attending to contingent differences between agents. In Kant’s anthropology, by contrast, head and heart capture how these faculties can be differently organised and their relevant material (cognitions and Triebfedern, respectively) differently proportioned (V-Anth/Busolt, 25: 1531) to yield agents with different personalities.
In summation, while Kant’s notion of the heart is not static over the years, a fairly consistent picture crystallises in the lecture notes up until 1788–9. The heart is the active side of the Sinnesart, or natural temperament. It contrasts on one side with Gemüth, which is its passive side, and on the other side with character, which is the active side of the Denkungsart based on freely chosen principles. Specifically, the heart is the power of the faculty of desire to generate Triebfedern in response to sensible feelings, which in turn ground desire. Which specific desires our hearts generate depends on their characteristic structure, i.e., how the agent’s Triebfedern are proportioned. For instance, if two agents experience the same displeasure, one might respond with avoidant withdrawal while the other responds with anger. In ordinary English, we might then attribute an anxious temperament to the first and an aggressive one to the second. Kant would concur, and simply add that the part of their respective temperaments which explains these differences is the heart.
Kant’s occasional references to Herz in his two main ethical texts (GMS, 4: 398, 410; KpV, 5: 85, 115, 152, 155, 156, 157) mostly conform to this model. Notably, in KpV Kant begins to explicitly mention the influence of the moral law upon the heart as a Triebfeder (5: 156), since he has articulated there how morality itself can be such a Triebfeder through the feeling of respect. However, Kant gives little indication there that he is invoking a well-developed notion from his anthropology. There is no attempt at definition, and the concept does no apparent systematic work. Insofar as it is an explicitly anthropological notion, arguably these ethical works are not the place for it; Kant sharply contrasts their projects with that of moral anthropology, which he brackets in both.
This makes it all the more striking, however, that the heart almost entirely disappears from the published Anthropology from a Pragmatic Point of View, which is largely a reworking of the earlier lectures.Footnote 12 The regular discussions of heart versus head, or comparisons with Gemüth and character, are absent from this work: those parts most reminiscent of them, like the early sections of the Characteristic, have been reworded to omit references to the heart. Kant no longer appears to think the term has a place in his anthropology. Instead, it has migrated to his writings on religion, to which I turn in the next section.
3. The heart in Religion
To understand the place of the heart in Religion, we should briefly review how Kant’s understanding of freedom evolves leading up to that work. In his first Critique, Kant argues that our actions are wholly determined by our ‘empirical character’ and the laws of nature (KrV, A539/B567). He makes room for freedom by arguing that our empirical character is in turn determined by our ‘intelligible character’, which is not subject to causal determination in space and time and therefore transcendentally free (KrV, A551/B579). Much ink has been spilled trying to understand the relation between these two characters. Noteworthy for our purposes, however, is that Kant uses Sinnesart explicitly as a synonym for empirical character and Denkungsart for intelligible character. In other words, Kantian freedom depends on the determination relation between the Denkungsart and the Sinnesart.
Kant’s subsequent moral works are often read as suggesting that the intelligible character directly determines individual empirical actions. Whether or not this reading is correct (I think it is not), in Religion Kant defends an apparently different understanding of the relation.Footnote 13 Since our motivations determine our actions, in order to be truly free and responsible for what we do, we must be responsible for those motivations. Kant now argues that we perform an ‘intelligible deed’ (RGV, 6: 31) of choosing a good or evil Gesinnung by subordinating one of our two fundamental Triebfedern, the moral law and our happiness, to the other in a supreme maxim.Footnote 14 He links this Gesinnung tightly to the Denkungsart (6: 30, 37, 38, 46). The choice to adopt an evil Gesinnung is, or grounds, the propensity to evil, which is the ‘ground for the possibility of an inclination’ to evil (6: 28; cf. Anth, 7: 265).Footnote 15 Thus, an intelligible choice for an evil maxim is the ground of empirical motivations. This holds equally for the intelligible choice for a good maxim, though this is more controversial, and I will not defend it at length here. Minimally, Kant thinks the choice to ‘change our heart’ from evil to good entails a commitment to cultivating morally beneficial feelings and motivations at the empirical level.Footnote 16 I will show that the heart plays an important role in Kant’s articulation of this picture. Kant’s argument for this role, as I understand it, is broadly transcendental. Given that we are capable of moral action, and moral action requires that we be responsible for our own motivations, we must have a power that makes this responsibility possible. To do so, this power – the heart – must be capable of bridging our intelligible and empirical characters.
Admittedly, Kant’s lack of an explicit definition of the heart makes this difficult to discern initially. The closest he comes to such a definition is the following:
the capacity or incapacity of volition [Willkür], arising from the natural propensity, to take up the moral law in its maxim or not, is called the good or evil heart. (RGV, 6:29)
This passage ties the heart into a very different conceptual network from that of the anthropology lectures. Though there is more consistency with the lectures here than meets the eye, we should first consider this new definition of the heart on its own terms. The reference to a ‘natural propensity’ may sound reminiscent of natural temperament, but in fact refers to the ‘natural’ propensity to evil introduced in the preceding sentence, which Kant goes on to argue is self-incurred by free choice. It is not obvious whether ‘maxim’ refers to the supreme maxim or to more particular maxims, or what to make of the idea that an evil heart is an ‘incapacity’ to take up the moral law into that maxim.Footnote 17 Regardless, the passage appears to suggest that ‘good/evil heart’ stands in for the agent’s moral status and is therefore interchangeable with ‘good/evil will.’
This view is problematic for two reasons, however. Firstly, Kant already has a well-developed notion of the will as practical reason (KpV, 5: 44, 55); he would not need to introduce ‘heart’ as another term. Secondly, Kant explicitly states they can come apart: ‘an evil heart … can coexist with a generally good will’ (RGV, 6: 37),Footnote 18 and one can have a ‘depraved heart, but still a good will’ (6: 44).Footnote 19 It is admittedly not obvious what a good will alongside an evil heart amounts to. We might explain it by characterising the will (Wille) as the autonomous lawgiving faculty, which is always good but not in control of the evil-hearted agent’s volition (Willkür).Footnote 20 Alternatively, we could read it aspirationally: the agent has a will that can be good, so that ‘there remains hope of a return to the good’ (6: 44).Footnote 21
Several off-hand characterisations Kant provides of the heart as a ‘ground’ of maxims promise more clarity:
-
A. [God], who sees through to the intelligible ground of the heart (of all maxims of volition). (6: 48)
-
B. the transformation of the Gesinnung of the evil human being into that of a good one is to be posited in the change of the supreme inner ground of the adoption of all his maxims, in conformity with the moral law, insofar as this new ground (the heart) is itself unchangeable. … the depth of the heart (the subjective first ground of his maxims) is inscrutable to [the human being] himself. (6: 51)
-
C. even the inner experience the human being has of himself does not let him see through to the depth of his heart in such a way that he could attain entirely certain insight through self-observation into the ground of the maxims which he professes and into their purity and stability. (6: 63, emphasis mine in each.)
This characterisation raises a new issue: it appears to equate the heart with the Gesinnung, which Kant also defines as ‘the first subjective ground for the adoption of maxims’ (6: 25). This equation is not immediately problematic. Unlike heart and will, heart and Gesinnung track one another: a good Gesinnung implies a good heart and vice versa, and the change of heart is also a change of Gesinnung. However, it once again raises the question of why Kant would introduce two separate terms, especially when both become central only in Religion, without clearly stating their identity.
Moreover, elsewhere Kant describes the heart in ways that do not fit the Gesinnung. A rich footnote addressing Schiller describes ‘the cheerful heart in complying with one’s duty’ (6: 24n).Footnote 22 If the heart harbours emotions like ‘cheerfulness’, it is not clear that the Gesinnung can. Kant also continues to contrast the heart with insight (6: 122), reason (6: 145), and understanding (MS, 6: 480) in ways that echo earlier contrasts with the head and locate it on the side of emotion and Sinnesart, whereas the Gesinnung is firmly on the side of Denkungsart. We thus need a reading which preserves the close connections both between heart and Gesinnung and heart and Sinnesart.
The key to this reading is in Kant’s description of the change of heart: ‘a revolution for the Denkungsart but a gradual reform for the Sinnesart’ (RGV, 6: 47). This is usually, correctly, read as claiming that a single, intelligible act of embracing the moral law in our supreme maxim manifests gradually in our empirical actions. However, we can now appreciate a deeper point: that a change in one thing, the heart, is a change in two different dimensions of agency, intelligible and empirical. Whatever the heart is, it must therefore encompass both dimensions. We know that pre-Religion Kant understood the heart entirely as part of the Sinnesart. His continued use of this word suggests he retains that understanding but now adds the Denkungsart to the heart as a new, moral dimension.
I propose that the heart now encompasses the active, i.e., desire-related, sides of both the Denkungsart and the Sinnesart. It relates them to one another: our freely chosen Gesinnung interacts with our natural temperament to produce our empirical desires. The heart is then Kant’s term for the relation between intelligible and empirical character. Simply having a term does not, of course, constitute an explanation of this relation. This is partly appropriate: Kant often emphasises the inscrutability of intelligible-empirical relations. However, understanding the continuity with Kant’s earlier analysis of the heart in the lectures will help us further unpack the relation and its implications for his action theory.
According to this earlier analysis, the heart is the power of the faculty of desire to produce Triebfedern. Specifically, the characteristic structure of our heart determines how our feelings cause Triebfedern, which in turn cause desire and action. There is no reason to think Kant abandons this picture in Religion. What has changed is that not only our Sinnesart but also our Denkungsart is included in this process. Specifically, whether our Gesinnung is good or evil now partly determines, alongside our natural temperament, whether or not feelings cause Triebfedern for us and how these are proportioned to others.
This change tracks an important shift in emphasis in Kant’s thinking about moral action. We saw earlier that, as his ethics develops, Kant increasingly emphasises the role of practical reason in choosing principles and the corresponding anthropological concept of character. By contrast, he downplays the ‘merely natural’ temperament, including feelings, as passively given to us. On a common intellectualist reading of Kant’s theory of moral action in the Groundwork, reason can determine the faculty of desire to actions merely through its judgement that the underlying maxims are morally right. It thereby stands completely separate from, and often opposed to, inclinations, which are based on feelings and have such low worth that it should be our ‘universal wish … to be entirely free from them’ (GMS, 4: 428). Kant’s earlier-cited Groundwork example of the cold-hearted philanthropist (4: 398) makes just this point. The philanthropist’s actions are not said to be morally worthy only if, or because, they are performed without sympathy in his heart. Rather, the example emphasises rhetorically that, regardless of his feelings or lack thereof, his reason enables him to act from duty.Footnote 23 Since his feelings are not under his control but the choice to act from duty is, only the latter is a source of moral worth.
However, later works increasingly suggest that Kant abandons his flirtation with intellectualism and still believes that all motivation requires feeling (KpV, 5: 75; MS, 6: 211; V-Met/Mron, 29: 877-8; cf. Frierson Reference Frierson2014: 56). In the second Critique, he elaborates the view that reason itself produces ‘moral feeling’ (KpV, 5: 76), namely respect for the moral law, as the ‘moral Triebfeder’ (5: 78), apparently because moral motivation too requires feeling.Footnote 24 In that same work, he begins to describe the moral law as exercising force upon the heart (5: 156). The Doctrine of Virtue goes further by introducing four ‘Aesthetic Preliminary Concepts [Ästhetische Vorbegriffe]’ of the ‘receptivity of the mind for concepts of duty in general’ (MS, 6: 399), which are subjective predispositions to various morally relevant feelings. Without these, Kant argues, we could not even be put under obligation. This is simply incompatible with the claim that reason alone suffices to make action from obligation possible. For moral action to nevertheless remain under our control, we must instead have some limited control over the feelings that motivate it.
Kant’s new view of the heart consolidates this picture of human beings as not merely passive, but active with regard to their feelings and the way they cause desires. The structure of our heart still partly depends on natural factors outside of our control. However, whether it is good or evil depends entirely on our chosen intelligible Gesinnung or Denkungsart and is therefore up to us. We partly determine how our faculty of desire responds to our feelings, i.e., which feelings cause strong Triebfedern and which leave us motivationally cold. We do so in two ways. Firstly, the feelings are now not merely coming ‘from outside’, as a result of our natural temperament and experiences. There are also feelings caused by reason itself, i.e., from an intelligible cause in our Denkungsart. Secondly, Kant’s description of the change of heart as a change in our Sinnesart implies that adopting a new Gesinnung can gradually alter our temperament. So while there remain ‘characteristic’ differences in temperament between individuals which yield differences in their actions, agents can also shape their temperament to reflect their moral outlook. For example, say an agent feels upset at being insulted. These feelings may cause Triebfedern to take morally impermissible revenge on the perceived wrongdoer, but only if that agent has the propensity to evil, which makes such inclinations to evil possible. This in turn depends on whether they have chosen an evil Gesinnung. Conversely, if they have a good heart, i.e., have embraced the moral law as their supreme Triebfeder to constitute a good Gesinnung, they will let the feeling of respect for the moral law act as a Triebfeder to make them a better person.
Summing up: in the Religion, the heart is still the power of the faculty of desire to translate feelings into Triebfedern. However, Kant abandons his attempts to argue that there could be another source of Triebfedern in judgement besides feelings. He is now wholly committed to thinking that all Triebfedern, including moral ones, are rooted in feeling and must, therefore, come from the heart. This does not mean that our moral judgement is motivationally irrelevant. Rather, by expanding the heart’s scope beyond the empirical Sinnesart to include the intelligible Denkungsart, Kant can say what he now realises his doctrine of freedom requires: that our choice of supreme maxim makes us responsible for our own motivations by determining whether we have a good or evil heart.Footnote 25
4. Implications and significance
Having established that in Religion, Kant has a distinctive concept of the heart as the power of the faculty of desire to produce Triebfedern on the basis of feeling determined by our intelligible and empirical characters, we can examine how it fits into his mature system.
Firstly, we can now understand the mysterious disappearance of the heart from Kant’s published Anthropology. ‘Pragmatic’ though this anthropology may be, it is still primarily descriptive: it catalogues natural properties of human beings without appealing to intelligible freedom. Kant’s early concept of the heart was such a property. However, in Religion, Kant has made the structure of the heart partly dependent on the agent’s free choice of intelligible Gesinnung. The heart connects this choice to their motivations. Kant, accordingly, now says of duty, the law, religion, and the will of God that they are ‘written’ or ‘inscribed’ upon the heart (RGV, 6: 84, 104, 159, 181). The heart has become a moral-anthropological concept connecting our intelligible freedom to our empirical nature. It therefore no longer belongs in a descriptive anthropology, but rather in the moral anthropology offered in Religion.Footnote 26
This shift also explains why the heart does not play a larger role in the 1797 Metaphysics of Morals. That work opens with a comprehensive exhibition of important concepts of Kant’s moral philosophy, especially those related to the faculty of desire (MS, 6: 211–4). One might think that if the heart is as important as I claim, we should expect to find it there. However, the introduction explicitly separates the metaphysics of morals from moral anthropology, ‘which would contain the subjective, impeding as well as favouring conditions in human nature for the fulfilment of the laws of [a metaphysics of morals]’ (6: 217). The heart includes elements of our sensible nature, which are subjective conditions; as a moral-anthropological concept, then, it does not belong in a strictly moral-metaphysical introduction to the faculty of desire.
Nevertheless, MS’s Doctrine of Virtue includes various references to the heart, most prominently in Kant’s discussion of ‘the first commandment of all duties to oneself’:
know (scrutinize, fathom) yourself … as regards your moral perfection in relation to your duty – your heart – whether it is good or evil, whether the source of your actions is pure or impure, and know what belongs either originally to the substance of the human being, or can be imputed to him as derived (acquired or incurred) and may belong to his moral condition. (6: 441)
This passage harmonises with my interpretation of Religion. It does so most clearly in its description of ‘acquired’ good or evil, which references our imputable propensity to evil, and in the immediately following characterisation of moral self-cognition as ‘trying to penetrate the depths (the abyss) of the heart’ (6: 441), echoing Religion’s descriptions of how God sees us. It is also clear, however, that Kant here takes heart neither to refer to mere sentimentality nor purely to moral character. The heart is ‘good or evil’ and ‘the source of our actions’, but in scrutinising it we may also find non-imputable elements that belong to us originally, i.e., our natural temperament. Its ‘purity or impurity’, which Religion explicitly describes as a condition of the heart (RGV, 6: 30), depends on the proportional relationship between our Triebfedern. All of this suggests that Kant is drawing on the account developed in Religion. He can permit himself to use the moral-anthropological concept of heart here, despite the strictures of the introduction, because the point of this section is not to give an account of that concept but to describe a duty we have to ourselves; and the task of a metaphysics of morals is the description of duties, regardless of the subjective difficulties we may encounter in fulfilling them.
The broader systematic upshot is that we can now understand Kant’s appeals to the heart in his mature works as supporting a theory of action in which the work of reason and feeling are not opposed but intimately related. Many interpreters might already assent to versions of this description. At minimum, however, in their defences of it, they have missed a term which is central to Kant’s own articulation of it. More ambitiously, appreciating that term’s significance helps us understand the workings of the faculty of desire, as well as other important aspects of Kant’s views, such as the change of heart, significantly better than we do now. In section 3, I have already laid out some of its action-theoretic implications: the activity of the heart is required for feelings to cause Triebfedern, and since reason’s decision for or against the moral law partly determines the heart we have, it is partly responsible for this activity and the resulting desires. At the same time, reason does not have absolute control: our natural temperament also determines how the heart produces desires, and we can only gradually change it. This explains Kant’s increased interest, from Religion onwards, in the affective requirements for moral action. To name just a few examples, he now suggests that agents who do their duty with a cheerful heart are truly virtuous, whereas those who do so with a hidden hatred in their heart will eventually fall short (RGV, 6: 24n.). Similarly, he calls ‘love’, that paradigmatic attitude of the heart, ‘an indispensable complement to the imperfection of human nature’ alongside respect (EAD, 8: 339). MS makes clear that virtue presupposes various moral feelings in the human being (MS, 6: 399–402) and that its development is a matter of cultivating strength to resist the inclinations (6: 405); i.e., a better proportion of Triebfedern in their heart.
5. Objections and replies
Even if the above arguments are successful, my account still faces at least two significant objections. The first draws into question its explanatory value; the second, its (con)textual plausibility. In this section, I address each in turn.
The first objection is that by identifying the heart as the power of the faculty of desire to turn feelings into Triebfedern, I have only named that power. I have not explained how it works or justified that it exists at all. This objection has two dimensions. Firstly, it threatens my claim to have unpacked the metaphor of the heart. Really, it seems, I have only identified its functional role in Kant’s system, not what the heart itself is. Secondly, and more significantly, it suggests that the action theory I attribute to Kant rests on an ad hoc foundation: the mere coining of a term which, by stipulation, makes us responsible for our motivation.
I partially share the worry. The textual material I have reconstructed here is limited and often indirect. While it is clear that Kant thinks there is a power referred to as the ‘heart’ which performs the roles I have described, of relating feeling to desire and bridging Denkungsart and Sinnesart, the textual material may not support a complete argument for this claim.
However, I suspect the objection just picks out a feature of Kant’s broader philosophical method. Kant thinks any philosophical system must begin from basic principles. In most contexts, he treats human faculties or powers, which must relate to one another to produce the distinctive materials – cognitions, desires, and feelings – of the human mind, as such principles.Footnote 27 Within this method, to identify a faculty or power of a faculty that shows how a given activity is possible as part of a system of human powers just is to explain that activity. The only way to then characterise this power is in terms of what it does. In the case of the heart, we may yet be tempted to insist on asking what the heart itself is because we recognise its very name as a metaphor. This, however, is a historical contingency. Kant takes the word from a tradition in which it is widely used and which originally more closely associated the capacity he is interested in with the physical organ that lends it its name. He gives no indication of being especially interested in this original connection. We should accordingly not treat the heart any differently from other powers, such as imagination, wit, or reason, all of which are in the final analysis derivative of the three basic faculties at the foundational level of Kant’s system.Footnote 28
Given this methodological framework, Kant employs a transcendental argumentative strategy. We already know that we perform some activity; if its possibility requires a particular power which relates our basic powers, then there must be such a power. It is no accident that Kant rarely, if ever, introduces powers into his system that are not already recognised in some form as a matter of folk or philosophical psychology, including the heart. He is aiming to systematise what we are aware of from our own experience and show what structure must underlie that experience in order for it to be possible. His criterion for the legitimacy of positing a power is whether it contributes to the unity of a system, whose elements agree with one another under common principles, as opposed to a mere aggregate (EEKU, 20: 206; cf. KrV A832/B860). Kant already holds in the lectures that since we act on the basis of feelings, there is a power relating feelings to desire, making such action possible, and that it corresponds to what people call the heart. He later realises that, given the requirements of his moral theory and the constraints of his system of faculties, moral action is only possible if this power is not only based in natural temperament but also equal to an intelligible choice of character. Since moral action is possible, the conditions for it must obtain, including a heart that bridges the intelligible and empirical characters.
I turn now to the second objection, which can be stated as a rhetorical question: if ‘heart’ is such an important term for Kant, why does he never introduce it as such? Though he defines it in the lectures, in Religion his characterisations are remarkably oblique. This reluctance suggests a more parsimonious explanation of his usage. As noted, the heart is a familiar metaphor in Christian cultural contexts. It was especially so within German Pietism, which styled itself a ‘church of the heart’ and which is Kant’s likely source for terms like ‘change of heart’. Foundational Pietist authors saw ‘living’ faith as grasped in the heart, not the head, and enjoined the cultivation of the heart (Francke 1690 [Reference Francke and Matthias2016]: 228, Reference Francke1723: 1.1; Spener Reference Spener and Aland1964: 35, 61, 80). Though Kant became sharply critical of Pietism, he was also a child and student of Pietists. When reflecting on religion in his old age, he may simply have thoughtlessly slipped back into the familiar vocabulary of his religious upbringing, without intending thereby to make a philosophically significant move.
We can only speculate about Kant’s intentions with regard to things he does not explicitly say. However, we already saw that, even in the early lectures, Kant’s central move is to define the heart as producing action. The heart does not merely feel but responds to feelings. His criticism of Pietism is that – on Kant’s own telling – it encourages passivity by valuing mere, ‘heartfelt’ sentiment over bringing about morally better conduct (RGV, 6: 172, 184n; SF, 7: 58). This suggests Kant is not simply repeating the Pietist view of heart but reappropriating it.Footnote 29 A more plausible explanation of his silence, then, is that he strategically chooses not to draw attention to this reappropriation. This strategy, I conjecture, is designed to draw in Pietist readers instead of alienating them.
Kant’s Critiques were aimed at a scholarly audience, which would expect clear definitions and refutations of earlier views. By contrast, Religion’s first parts were published in the Berlinische Monatsschrift, a magazine for the general educated public (Beiser Reference Beiser1993: 166). Kant insists in the Preface that its ‘essential content’ is accessible to anyone, like ‘children’s education or sermons’, and calls it ‘readily understandable’ (RGV, 6: 14). Comical though his self-assessment is, we should take Kant’s intentions seriously. Though Religion is occasionally polemical, its project is fundamentally ecumenical: readers with ‘common morality’ should find in it the rational core of a faith they already recognise.
This ecumenism would certainly have extended to Pietist readers, many of whom had been near and dear to Kant. Familiar-sounding references to the heart would bring them into his project by language they could relate to. Kant thereby highlights the continuity of his project with theirs, while subtly shifting the meaning of its central terms. This would make Pietist and other readers more likely to give Religion a fair hearing. By contrast, explicitly redefining ‘heart’ and drawing attention to the difference would hurt this aim. Given all the evidence above that Kant attached clear philosophical meaning to this term, this story would make better sense of Kant’s reintroduction of that term in this work in particular.
6. Concluding thoughts
We can now answer each of the three questions posed at the beginning of this paper. Firstly, for Kant, ‘heart’ is a distinctive technical term, irreducible to any other in his anthropology. It refers to the power of the faculty of desire to translate feelings into desires, which is determined both by our intelligible Denkungsart and our empirical Sinnesart. Secondly, Kant initially treats the heart as part of our merely natural temperament, which is largely irrelevant to his mature ethics. In Religion, however, he sees that his doctrine of freedom requires that we be responsible for our own motivations. He therefore introduces an enriched notion of heart into his moral anthropology, which relates our intelligible choice to our empirical motivations. Thirdly, the heart is significant in Kant’s moral philosophy insofar as it supports a theory of action on which feeling is required for all motivation, including moral motivation; but we are responsible for how we transform feeling into motivation. Morality, that is, speaks to the whole heart.
If the exegetical arguments of this paper are successful, interpreters should abandon the default view and take Kant’s references to the heart not only in Religion but also across his work more seriously than they typically have. In closing, I want to draw attention to a wider philosophical upshot. Seeing that Kant had a well-developed notion of ‘heart’ demonstrates that this metaphor can be given specific, philosophically interesting meaning. From a historical perspective, this is unsurprising; indeed, Kant’s is far from the only available account in the tradition. In recent moral philosophy, however, this fact appears to have been largely forgotten.Footnote 30 Stephen Darwall has recently pointed out a heart-shaped gap in contemporary moral philosophy. Analytic philosophers have been reticent to talk about the heart due to its ‘unavoidably metaphorical’ appearance; they ‘look for cash to underwrite metaphorical promissory notes’ (Darwall Reference Darwall2024: 1).Footnote 31 Whether Kant’s notion of the heart in particular would best fill this gap is a subject for another paper. That we can fruitfully cash out the metaphor even in a system like his, however, suggests we should not take heart-talk for granted. We have more to gain from thinking about the heart than philosophers have often supposed.
Acknowledgements
This paper owes much to feedback and encouragement by Eric Watkins, to whom I am tremendously grateful. I also want to thank Lucy Allais, Lis Benossi, Andrew Chignell, Anna Connell, Davide Dalla Rosa, Kristina Engelhard, Rima Hussein, Steve Naragon, Cristián Rettig, Konstantin Pollok, Lorenzo Spagnesi, Yvonne Tam, Jens Timmermann, and Clinton Tolley for valuable discussion and feedback. Finally, I am grateful to audiences at the Research Colloquium at the Universität Trier; the 2025 ‘Love, hate, and reactive attitudes’ conference at Boston University; the Johns Hopkins University History of Philosophy Group; the LSR Seminar at the Princeton University Center for Human Values; the 2025 Pacific Division meeting of the APA; and the 2024 North American Kant Society Midwest Study Group at Marquette University/University of Wisconsin-Milwaukee for their questions and comments.
Open access
