The volume honours Paul Guyer’s impact on Kantian studies. It is fair to say that much of Guyer’s contribution to the literature casts light on the relationship between Kant’s account of freedom and nature. Kate Moran, the volume’s editor, explains her choice of title for this collection by noting the generally plausible idea that Kant’s notion of spontaneity is central to his account of nature (pp. 1–3): After all, Kant repeatedly claims that the spontaneity of the understanding is the origin of the laws of nature (as at A126–7 and CPJ 5: 186–7). Thus, analysing the relationship between Kant’s account of freedom and nature should at least indirectly relate the relationship between freedom and spontaneity. By way of reflecting on how, precisely, Kant’s account of the spontaneity of the understanding relates to his account of the relationship between freedom and nature, I will here focus on three of the chapters in the volume, namely, those by Guyer himself, Brian Chance and Karl Ameriks.

First, however, I should note that the volume contains a number of valuable essays that thematically hang well together. Jennifer Dobe, for instance, offers a novel interpretation of Kant’s principle of the judgement of taste as a social and thus contingent principle. Similar themes about Kant’s relationship to the contingency of human nature are explored in chapters by Kate Moran and Barbara Herman. Lucas Thorpe advocates a similar idea by arguing that some of the enabling conditions for the capacity to recognize the humanity of others are social (and to that extent, contingent). Patricia Kitcher gives a novel account of the role of ‘promoting the happiness of others’ as a value that is central to Kant’s ethics. In one way or another, all these chapters are influenced by Guyer’s general insight that Kant’s philosophy is more sensitive to natural and social conditions of humanity than Kant’s critics allow. Additionally, a set of excellent meta-ethical chapters discuss constructivism and moral realism in Kantian ethics (by Julian Wuerth and Frederick Rauscher), and two engaging chapters on Kant’s political philosophy explore his conception of freedom in that context (Allen Wood, and Michael Nance and Jeppe von Platz). The volume also includes a précis of Rolf-Peter Hortsmann’s recent work on Kant’s account of imagination (also reviewed in this issue), and Michael Rohlf’s careful analysis of the relationship between transcendental idealism and the B-Deduction.

Guyer’s closing statement in this volume nicely captures the central theme of his interpretation of Kant over the years: ‘Kant always assumes a gulf between nature and freedom, but never an unbridgeable gulf’ (p. 294). Let me quickly (and briefly) unpack this claim. Put broadly, Kant assumes a ‘gulf’ between freedom and nature in that he assumes a sharp distinction between noumena and phenomena. Whether we understand the distinction as epistemological, metaphysical or ontological, it is rather uncontroversial that, for Kant, freedom can only be a property of noumenal things, while the laws of nature only govern phenomena. Thus, he holds that there is a gulf – a sharp epistemological, metaphysical or ontological distinction – between things that can be brought under the concept of freedom and natural things. Many of Kant’s critics and sympathetic readers agree that both Kant’s theoretical and practical philosophy demand the possibility of ‘bridging’ this gulf. His critics, of course, argue that the bridge cannot be built but Kantians beg to differ. What is this demand, then, and why might it be a problem?

In the theoretical case, Kant often talks about a grounding relationship, claiming that (empirically real) phenomena must be grounded by noumena (cf. A537/B565). Thus, on the one hand, Kant wants to make a sharp distinction between phenomena and noumena. On the other hand, if this distinction is too sharp, then it would be difficult to see how one could ground the other. In his chapter, Guyer notes that the ‘bridging’ problem in Kant’s practical philosophy concerns a grounding relation, too. For Kant’s moral philosophy to work, we must be able to make sense of ‘the idea of free decisions in the noumenal world causing actions in the phenomenal world’ (p. 279; emphasis added). But since Kant limits the scope of the category of causation to phenomenal reality, Guyer explains that we can make sense of the practical ‘causing’ relationship between noumena and phenomena only in terms of grounding. So, again, on the one hand, Kant wants to maintain a grounding relationship between noumenal activities and their phenomenal correlates. On the other hand, Kant also holds that there is a sharp distinction between noumenal mental activities and their correlating phenomena. For instance, Guyer notes, whereas phenomenal mental activities are temporally ordered (decision A comes after decision B, etc.), no temporal order can be attributed to noumenal mental activities (p. 286). But if so, then perhaps the distinction between phenomenal and noumenal mental activities is also too sharp to make sense of the idea of one grounding the other. That spells trouble for Kant’s practical philosophy.

For the most part, Guyer’s postscript in this volume is a successful attempt to show that ‘from 1781 to 1790 (and beyond, into his final uncompleted work)’, Kant assumes that the gulf between nature and freedom is bridgeable (p. 293). In particular, he argues that the desiderata of bridging this gulf ‘was not a new idea in the third Critique’ (ibid.). For instance, reflecting on the earlier practical writings, Guyer notes that by Kant’s own lights, ‘the act of setting ends does not take place in some purely [noumenal] mental space, but in the natural world, and in this regard there is already a bridge between the domain of freedom and the domain of nature’ (p. 276; my emphasis). Of course, Kant’s critics won’t be satisfied. After all, they also insist that, by Kant’s own lights, we can make sense of the act of setting ends only if we bridge the gap between nature and freedom. However, they maintain that Kant has made the distinction between freedom and nature (i.e. noumena and phenomena) so sharp that he cannot bridge that gulf. In that sense, one might think, Guyer’s modus ponens is Kant’s critics’ modus tollens.

However, in Chance’s chapter, we can find the outlines of an interpretative strategy for showing how Kant could actually bridge this gap via his notion of the spontaneity of the understanding. Chance argues that Kant’s conception of the spontaneity of the understanding is developed in direct response to Christian Wolff’s view. According to Chance, on Wolff’s account there is no pure use of the understanding: that is, the understanding cannot provide original content, but rather only produces content by processing representations that are already presented to it by the senses. In this context, Kant’s thesis of the spontaneity of the understanding is best understood as a direct denial of the Wolffian thesis. ‘Thus’, Chance writes, ‘when Kant describes the understanding … as “the ability to bring forth representations itself”, and then glosses this ability as the “spontaneity of cognition”, he is implicitly contrasting this account of the understanding with the Wolffian one according to which the understanding is not an independent source of representation’ (p. 41).

Now, consider Guyer’s account of the relationship between the Wolffian and Kantian account of reason from one of his earlier writings:

In contrast, Guyer writes, ‘Kant transforms the traditional and Wolffian conception of reason as a power of insight into connections existing independently of our thought and action into a conception of reason as a power to create order by our thought and action’ (Guyer Reference Guyer2017: 79).

To be sure, Guyer puts his point in terms of reason, and consequently, he adds that ‘[n]owhere are the implications of this transformation clearer than in Kant’s practical philosophy’ (Guyer Reference Guyer2017: 79). However, as Chance rightly notes, it is easy to see how Kant’s critique of the Wolffian tradition’s conception of reason is mirrored in his critique of that tradition’s account of the understanding (p. 47). On the Wolffian account, our understanding is not an original source for imposing order onto empirical reality; rather, the understanding seeks to find an independent natural order. But Kant’s commitment to the spontaneity of the understanding is a commitment to the idea that our understanding is the ultimate source of the laws of nature (cf. B163–5).

Recall that the relationship between phenomena and noumena, both in the theoretical and practical contexts, concerns a grounding relationship. According to a recent account, Kant holds that noumena ground phenomena in that the laws of the phenomenal world are determined by noumena (see Watkins Reference Watkins2005: ch. 5). If one were sympathetic to this reading, then the central point of Guyer’s chapter is reconfirmed. After all, Kant’s idea that the spontaneity of the understanding grounds the laws of phenomenal reality is a centrepiece of the first Critique. Thus, right from the beginning of his Critical period, Kant maintained that there is a gulf between nature and freedom, but a bridgeable gulf. There is a gulf because, arguably, the spontaneity of the understanding is a feature of the noumenal activity of our minds which is not determined by sensible conditions. In other words, spontaneity of the understanding amounts to mental self-determination or freedom, and thus does not belong to the phenomenal world. And the gulf is bridgeable because the laws of the phenomenal world are ultimately determined by that noumenal self-determination of the mind. Finally, Kant’s argument for this claim (that the gulf can indeed be bridged) is one and the same as Kant’s argument for the claim that the spontaneity of the understanding is the source of the laws of nature, i.e. his argument in the Transcendental Deduction.

In the previous paragraph I identified the activity of spontaneity of the understanding with noumenal mental ‘freedom’. However, remember that we are trying to show that, on the Guyer/Chance reading, the notion of the spontaneity of the understanding can be employed to explain Kant’s way of bridging the gulf between nature and freedom, presumably in the practical sense. Yet, the notion of freedom employed in the above context seems to be different from the practical notion of freedom. To be sure, there is a sense of ‘self-determination’ that can characterize the spontaneity of the understanding (as Moran discusses; cf. p. 1). But as Karl Ameriks rightly warns us in his chapter, Kant’s practical conception of freedom as self-determination ‘is neither a matter of overly subjective arbitrariness nor overly objective mere subjection to laws’ (p. 193). Insofar as Kant’s account of the spontaneity of the understanding is concerned there does not seem to be a major concern with overly subjective arbitrariness. However, while Kant does maintain that the understanding is spontaneous in imposing an original order onto nature, the order that it can impose is absolutely objective. That is, Kant does not think that it is ‘up to us’ to determine the order of nature in this or that way, although we determine the order of nature.

I close with this: on the one hand, Chance rightly points out that Kant’s notion of the spontaneity of the understanding plays a central role in explaining how the gap between noumena and phenomena could be bridged. Accordingly, Guyer is right to point out that, throughout the Critical period, Kant held that there is a bridgeable gulf between the noumenal and the phenomenal worlds – indeed, this idea is presented in the notoriously difficult but central section of the first Critique, the Transcendental Deduction. On the other hand, it remains an open question whether the spontaneity of the understanding can also explain Kant’s attempt to bridge the gap between freedom (in the practical sense) and nature. For the latter strategy to work, one must be able to show a meaningful link between the spontaneity of the understanding and the capacity of practical reason for ‘self-determination’ – that is, as Ameriks points out, self-determination not in an overly objective nor overly subjective manner. It remains an open question how, or whether, Kant could account for practical self-determination via the notion of spontaneity.