According to Kant, the demands of morality are universal and necessary. Yet he also contends that practical reason’s progress is embedded in a process of historical development, raising several questions. How does the universality and necessity of moral demands square with the particularity and contingency of empirical circumstances? What are the historically situated socio-political conditions of reason’s progress? How does the individual exercise of practical reason relate to humanity’s collective progress?

These and related questions are addressed in Olga Lenczewska’s Cambridge Element, Kant on the History and Development of Practical Reason. The Element not only offers a clear overview of Kant’s account of the historical development of practical reason but also advances an original scholarly contribution. In what follows, I outline the book’s central claims and engage critically with Lenczewska’s interpretation.

Lenczewska argues that Kant’s account of humanity’s progress is best understood in connection with his speculative account of the emergence of rationality. In doing so, she foregrounds the significance of Kant’s ‘Conjectural Beginning of Human History’ (1786) and situates it within Kant’s critical project. She develops this interpretation across three sections, from the transition from ‘nonrational animals’ to rational human beings, to the systematic role of Kant’s conjectural history, and finally to the socio-political conditions of reason’s historical development.

In Section 1, Lenczewska draws on Kant’s anthropology lectures and the ‘Conjectural Beginning’ to reconstruct his account of human animality and the development of rational capacities. Rationality, she argues, arose from the comparison of natural desires, progressing from instrumental reasoning to control over natural impulses – especially sexual instinct – then to the anticipation of future outcomes, and finally to a (still indeterminate) grasp of humanity’s moral vocation. Lenczewska connects this developmental trajectory with Kant’s conception of practical egoism in Anthropology from a Pragmatic Point of View (1798), understood as the disposition to treat one’s own happiness as the supreme determining ground of the will, and maintains that this orientation characterises humanity in its infancy. Against this, she invokes pluralism – the standpoint of regarding oneself as a citizen of the world – as the normative counterpoint. On her account, the history of reason’s development thus traces the progression from an initial condition of practical egoism toward the standpoint of pluralism.

Section 2 turns to Kant’s ‘Conjectural Beginning’, situating it within both the genre of eighteenth-century conjectural histories and the framework of critical philosophy. As Lenczewska emphasises, these contexts are illuminating: understanding the conventions of the genre is essential for grasping what Kant is doing in the text and how it fits within his broader philosophical project. She provides a concise overview of the genre’s defining features to show that Kant largely brackets questions of historical accuracy, instead offering a teleological account of humanity’s emergence from prehistoric nature that is methodologically conjectural yet ‘useful from the practical perspective’ (37).

Section 3 explores the socio-political conditions of reason’s maturation through the concept of pluralism. Lenczewska contends that humanity’s progression must be ‘achieved via two separate, but mutually reinforcing processes: one internal (arriving at the disposition to pluralism within every human being) and one external (arriving at the political condition of cosmopolitanism)’ (47). She develops the internal dimension by connecting the pluralist disposition to the three maxims of common understanding – thinking for oneself, thinking from the standpoint of others, and thinking consistently – and by relating it to practices of communication and the public use of reason. Given Kant’s commitments to both individual maturity and universal enlightenment, Lenczewska identifies education as the key factor connecting personal development and collective progress. On her reading, teachers as well as religious and political leaders are tasked with instilling these maxims as widely as possible, thereby fostering a gradual, intergenerational trajectory toward pluralism. At the same time, this prospect is significantly constrained: Lenczewska attributes to Kant the view that only ‘Occidental whites’ are capable of this mode of thinking and that only they inhabit societies that enable it (58). This restriction notwithstanding, Kant treats pluralism as a necessary condition of a just juridical order and of humanity’s rational maturation.

Lenczewska’s reconstruction is innovative and thought-provoking, bringing into view connections that have received little sustained attention in the literature. At the same time, several aspects of this interpretation invite closer scrutiny.

Lenczewska provides an insightful discussion of the genre of conjectural history and the place of Kant’s ‘Conjectural Beginning’ within it. She rightly emphasises the speculative character of such narratives, which attempt to reconstruct the prehistorical existence of human beings on the basis of limited empirical evidence. However, her linguistic analysis of conjectural history is less convincing. She identifies a ‘particular verb tense’, the ‘conjectural necessary’, allegedly ‘used to denote events that might have or must have taken place in the past’, and explicitly characterises it as a ‘grammatical tense’ distinct from the simple past and past perfect (33). Yet, this conflates grammatical tense with epistemic modality. The distinctive feature of conjectural history is not a special grammatical tense but the systematic use of modalised past constructions (e.g., ‘must have’ and ‘might have’) to mark claims that are not directly evidenced but are licensed as necessary or plausible given a theoretical reconstruction. This linguistic issue notwithstanding, there is a modal confusion in calling this epistemic modality the ‘conjectural necessary’, since what ‘might have or must have taken place in the past’ (33) expresses both possibility and necessity.

This modal ambiguity has consequences for understanding the epistemic force of Kant’s claims in the ‘Conjectural Beginning’. Kant himself characterises the essay as a ‘pleasure trip’ and a ‘flight … on the wings of the power of imagination (8: 109), and Lenczewska notes that the account is ‘merely possible from the theoretical perspective’ (37). Yet, it remains unclear what modal status these claims enjoy from the standpoint of practical reason. On the one hand, she argues that ‘we are permitted, from the practical philosophical standpoint, to think of our rational capacities as having emerged in a way described in this essay’ (8) and that such a reconstruction is ‘useful from the practical perspective’ (37), suggesting that practical reason allows for, but does not require, conceiving of our rational development in these terms. On the other hand, she also claims that the essay ‘sheds light on the nature of these capacities’ (7, 37), implying that at least some features of the reconstruction are necessary for understanding the structure and development of rationality. It remains unresolved, in Lenczewska’s reading, whether Kant’s conjectural history is merely a practically useful representation of humanity’s development or whether practical reason itself requires us to conceive of our rational development in broadly these terms, despite its theoretical unverifiability.

Lenczewska’s interpretation of Kantian pluralism as grounded in the three maxims of common understanding is both original and intriguing. However, some aspects of this interpretation appear to outstrip their textual support. In particular, she identifies the second maxim – thinking from the standpoint of others – with the public use of reason (51–5). According to Lenczewska, Kant holds that ‘individuals in public positions must only use reason in a private sense, meaning their reasoning is limited by an authority outside of reason itself’ (53). Yet, the restriction of public figures to the private use of reason is too strong and sits uneasily with Kant’s own examples in ‘What is Enlightenment?’. There Kant explicitly argues that the military officer, the taxpaying citizen, and the clergyman must restrict the use of reason only insofar as they act in their official capacities, while remaining free to make a public use of reason ‘as a scholar before the entire public of the world of readers’ (8: 37). The distinction is thus primarily institutional: the use of reason is defined in relation to the socio-political structures within which it is exercised, either within the confines of an office or before the reading public independently of that role.

Moreover, Lenczewska claims that the public use of reason involves attending to ‘the formal and necessary features of human rationality’ (53). By identifying the public use of reason with thinking from the standpoint of others, however, she conflates a socially situated form of rational activity with the epistemic norms governing it. Indeed, viewed against the backdrop of egoism – the counterpart to pluralism in the Anthropology – we can readily imagine a scholar who submits writings to the broader public and yet deems the judgement of others unnecessary as an external criterion of truth (7: 128). Academia, I suspect, offers no shortage of examples. That said, there may well be an important connection between the second maxim of common understanding, the public use of reason, and pluralism, though establishing it would require more argumentation than Lenczewska provides.

Finally, Lenczewska’s treatment of Kant’s racism is underdeveloped. In recent years, Kant’s views on race and their relation to his moral and political philosophy have become the subject of extensive scholarly debate. Yet, Lenczewska’s discussion relies almost entirely on Lu-Adler’s interpretation, leaving unaddressed a substantial body of recent literature on the topic. Moreover, Lenczewska does not engage in any sustained way with the relevant Kantian texts themselves. Her remarks therefore remain more programmatic than scholarly.

Despite these concerns, Lenczewska’s study raises a number of important and underexplored questions concerning the historical development of rational agency in Kant’s philosophy. Her interpretation integrates Kant’s conjectural history, anthropology, and account of Enlightenment into a unified conception of practical reason’s maturation that is ambitious and often illuminating. The Element ultimately makes a rich and distinctive contribution to ongoing discussions of Kant’s practical philosophy and philosophy of history.