In this concise and tightly argued monograph, Jennifer Mensch has demonstrated, first, Kant's continual and critical attentiveness to the work of the emergent life sciences across the eighteenth century. She shows a clear grasp of what that scientific work took up and what its philosophical implications were – both for the scientists and for Kant. Others have mentioned this aspect of his intellectual background. Long ago, the great Kant scholar Erich Adickes developed an extensive treatment of Kant als Naturforscher. But more recent interpreters of Kant have taken a more limited view of Kant's scientific interests. Restriction to the so-called ‘exact sciences’ has, whether deliberately or tacitly, downplayed this life-science dimension in Kant's intellectual development. Much that was missed by this election Mensch has succeeded in bringing to light. Central, here, is the notion of epigenesis in the emergent life sciences, articulated by thinkers like Buffon, Maupertuis and C. F. Wolff, and contested by such figures as Haller and Bonnet. Mensch traces carefully and compellingly Kant's study of this question from the 1760s to the 1790s. Her account of how Kant came to understand the thinking of the naturalists over the course of the eighteenth century and relate it to his own quest for a transcendental ground of reason in self-generation is very well wrought.

It is this second aspect of appropriation that is most striking and original in the work. That is, Mensch contends that Kant was not only aware of the development of the idea of epigenesis in the theory of biological generation and development, but that he systematically exploited the potential of this way of thinking for his transcendental philosophy. Thus, she argues that the first Critique is most fruitfully read from the closing passages of the work, which develop an extensive analogy between the architectonic of reason and the form of living organisms (A833/B862). Hence her title, ‘Kant's organicism’. Mensch presses this analogy to the very centre of the transcendental philosophical endeavour in Kant, as the ultimate grounding for the transcendental argument itself: ‘the overriding importance of organic models for Kant's conception of reason’ (125). For her, one must underscore, this is a metaphysical conceptualization of the nature and self-developmental force of pure reason. ‘Ultimately, Kant was a metaphysician with respect to reason, and because of this he was able to think about reason as something self-born’ (159 n. 13). Mensch notes Kant's unique but important usage of the term Selbstgebärung of reason at A765/B793 (133 n. 280, 212). Kant believed metaphysics could only be renewed if it could free itself from the reciprocal weaknesses of empiricism and innatism in the theory of rational process and warrant. Mensch contends that Kant could accept neither the Lockean claim that concepts arose reflectively from sense experience nor the Leibnizian notion that they were in some sense fully ‘preformed’ or pre-established in the mind, with echoes of the ‘innate ideas’ of Descartes and the ‘intellectual intuitions’ of the Platonic tradition. Neither empirical experience (nature) nor God could account for reason's force without compromising Kant's essential commitment to human freedom. ‘The fact of human freedom, according to Kant, meant that the basis of our particular cognitive unity had to be generated by us’ (107).

Mensch contends Kant was attracted to the crucial importance of self-formation as a theoretical idea in the life sciences. That was the essential feature of epigenesis: ‘the very basis of Kant's long-standing attraction to epigenesis was its ability to position the mind's independence from both sense and God as suppliers of mental form’ (214–15 n. 283) Thus Mensch's historical reconstruction of Kant's Critical turn moved ‘From Original Acquisition to the Epigenesis of Knowledge’ (80ff.). ‘Only once intellectual concepts and the ideas of reason could be traced back to their birthplace in reason, only after reason could itself be identified as “self-born” and containing the “germs of its self-development,” only then could knowledge be secured and the dogmatist and the sceptic alike refuted’ (139). ‘Only … appealing neither to experience nor to God but only to itself, could [reason] serve as the true ground of experience’ (139).

Most obviously, Mensch aims to make sense of the provocative passage at B167 of the first Critique where Kant wrote of an ‘epigenesis of reason’. She argues that, while Kant never believed that as empirical life science such an approach could be recognized as objective, paradoxically it could be used to explain the self-constitution of reason and the warrant for knowledge. The key argument of Mensch's work is: ‘Kant embraced epigenesis as the model for understanding the metaphysical generation of reason and the categories alike’ (214 n. 283). Indeed, ‘the epigenesis of reason … was far more radical than the one Kant was willing to accord natural organisms’ (15). That is a remarkable finding, and one that is, to the best of my knowledge, quite original. I think it makes sense of many elements in Kant that otherwise seem incongruous. Her work should rouse a lively discussion in Kant studies and in the history of the life sciences.

But what about the life sciences themselves? ‘Kant was consistent … in rejecting positive discussions of epigenesis as a phenomenon of nature … ’ That is, ‘while Kant seems to have thought it was reasonable to choose from organic models of generation when describing the epigenesis of reason, he would never have suggested that such a model was definitively at work in the actual generation of natural organisms’. He ‘did not believe we could make anything like an identical claim regarding the laws by which an actual organic being might work’ (141). Thus, ‘Kant credited Buffon with having provided a “natural system for the understanding” … But his account had not achieved the status of a genuine natural history … Buffon's mistake, from Kant's perspective, was concentrating on a physiological explanation of the origin, degeneration, and even potential reversion of varieties’ (100–1). That is, Buffon was trying to do life science, while Kant took it to be an impossible endeavour. ‘He was pessimistic regarding any possibility of progress in generation theory … embryogenesis … simply exceeded the limits of our claims to knowledge of such things’ (53). That is, ‘the operating principles of the organism would simply never be revealed in an empirical investigation’ (144). Hence, in my terms, what Mensch demonstrates is that Kant arrogated a biological theory from its own precinct as empirical science, which he declared theoretically unjustified, for a metaphysical theory of pure reason, where he took it to be not only justified but indispensable. Indeed, he came to allege that the very biological formulation he annexed had all along been parasitic on reason's own self-conception, thus working by illicit analogy, or, in his terms, ‘subreption’. As Mensch puts it, ‘when reason saw organic activity in nature, according to Kant, what it was really looking at was itself’ (144).

In the course of her account, Mensch draws an intimate connection between the ‘unity of reason’ and what she calls the ‘unity of race’ in the context of the publication of Kant's first essay on race (1775/77). Quite correctly she highlights the multiple perplexities in accounting for this publication in the context of Kant's notoriously ‘silent decade’ (95–6). She asks: ‘What had Kant discovered in 1775 that he felt it necessary to announce?’ (96) and she replies: ‘the discovery worth announcing in 1775 was … the positive explanatory role that could be played by teleology in a rationally unified order’ (106). This is interesting, perhaps even plausible, but it does not suffice, in my mind, to account either for the course announcement of 1775 or, a fortiori, for its revised republication in 1777. Moreover, I find myself sceptical of her acceptance of Kant's description of his theory of Keime and Anlagen as ‘merely advancing an “idea” intended for “useful academic instruction,” a mere preparatory exercise contributing to an enlarged “pragmatic knowledge of the world” … ’ (99). Mensch suggests ‘Kant was adopting a new methodological stance … capable of philosophical speculation into the forbidden territory of biological origins … while yet avoiding the epistemic pitfalls of subreption’ (99–100). Here, rather, I think we need to take Kant's pretensions as a Naturforscher a bit more seriously. As his controversies with Herder and above all Forster in the 1780s betoken, Kant took himself to be making a scientific claim, not just a pedagogical gambit. Mensch herself notes: ‘According to Kant, the only way to explain environmental adaptation was to suppose the preexistence within species lines of “germs” for new parts and “natural dispositions” for proportional changes to existing parts’ (11; my italics). That was a scientific hypothesis, and Kant reacted fiercely in the 1780s to defend it as such. Raphael Lagier, Les races humaines selon Kant (2004), seems more apt on this score.

Finally, I am not as sanguine as Mensch appears to be that Kant is the best philosophical lineage with which to connect recent work in epigenetics and emergent properties. As she herself puts it, ‘Kant was in the end a metaphysician, and his own species of organicism would therefore have to be nonnaturalistic’ (124). Moreover, his attitudes about the possibilities of empirical biology were excessively restrictive. I cannot agree with Mensch about the prominence of ‘boundary maintenance’ for the emergent sciences of the late eighteenth century or as the ‘key to their successful embodiment in each case’ (216 n. 287). I take this for less a ‘vanguard’ posture than a conservative one. It was not a failing that the life scientists of his time and thereafter ignored his insistence upon the constitutive/regulative distinction and his warnings against any ‘daring adventure of reason’ in conceptualizing or empirically pursuing genealogical or organic development. From Blumenbach through Goethe to Darwin, as Mensch herself acknowledges, life science would need to free itself from Kant's constraints to undertake its empirical and theoretical work. And that, I submit, is still more the case today.