In this dense, tightly argued book, Tom Rockmore offers the reader a rapid jaunt through German Idealism, following the red thread of constructivism as a response to the problem of cognition (das Erkenntnisproblem). At times, the pace of Rockmore’s overview is dizzying. One rips through in a few dense pages treatments of secondary figures such as Reinhold, Maimon and Schulze, and even the principal protagonists receive brisk analyses. It is not until the penultimate chapter that the pace slows and the rapidity of exposition gives way to a more detailed and synthetic approach. With Rockmore’s discussion of Hegel, the tone of the work changes as we move from an almost encyclopaedic recounting of books, treatises, reviews and letters to a more systematic reconstruction of the development of Hegel’s epistemology. Retrospectively, the book’s structure becomes clear: the problem is formulated and the constructivist solution is announced in Kant’s famous Copernican revolution (Introduction and Chapter 1). This epistemic breakthrough is then reconsidered through the lens of several attempts to expand, clarify, ground, systematize or otherwise improve on Kant’s original insight that we know only what we construct (Chapters 2–4). This contested array of theories, systems and critiques then sets the stage for the drama’s denouement, i.e., the comprehensive solution found in Hegel—the hero of Rockmore’s story (Chapter 5).

But why one more book on German Idealism? Isn’t the field already so populated that the main thrust of this philosophical movement is bound to be clear? Rockmore answers in the negative. The field is, in fact, a hopelessly confused and tangled mess. The lack of scholarly consensus is due first and foremost to the great complexity, originality and fecundity of the thinkers under discussion. Not only do Fichte, Reinhold, Maimon, Schelling and Hegel disagree about the core of Kant’s transcendental idealism, but their own positions are continually shifting as they probe more deeply into the knowledge problem. Compounding this difficulty is the self-presentation of each thinker. Fichte, Schelling and Hegel all first present themselves as disciples following the master’s lead, then as fulfilling the deep intention of their forerunner, and finally as offering an original but comprehensive solution to the fundamental problem.

In light of such considerations, the lack of contemporary interpretative consensus should hardly come as a surprise; but the disagreement is not just over superficial details. Prominent scholars such as Beiser, Pinkard, Horstmann and Franks disagree about who even counts as an idealist. What then does Rockmore hope to achieve in this short book? Nothing less than a perspective on the whole movement of thought from Kant to Hegel that illuminates German Idealism’s animating question and explains its most significant philosophical insight—constructivism as a response to das Erkenntnisproblem.

In formulating the problem, Rockmore pays particular attention to Kant’s remarks on Plato, which he argues help us see the cognitive problem to which the critical philosophy responded (4). According to Rockmore, Plato’s conception of knowledge as the achievement of ‘the identity of thought and being’ presupposes ‘first, there is mind-independent reality; second, thought (or thinking) can grasp mind-independent reality as it is beyond appearance; and third, when we know, thought in fact grasps mind-independent reality as it is’ (168). In response, only two epistemic strategies appear possible: one either starts with the appearances and ascends to being or one leaps over the appearances and immediately grasps the reality behind them—tertium non datur.

Kant’s brilliance lies in cutting through this apparently exhaustive disjunction. His third route, Rockmore argues, is key to German Idealism, the core of which is a philosophy of ‘identity in difference’—‘a metaphysical relation brought about by the subject in creating a unity between itself and the object it “constructs”’ (5).

Rockmore’s treatment of Kant focuses on the Copernican revolution and the Transcendental Deduction. Rockmore regards the latter not only as an attempt to ground the validity of the categories, ‘but above all as a constructivist approach to cognition’ (8). The first hurdle to overcome is the conventional reading of Kant as a representationalist. According to Rockmore, this reading fails to adequately address the full significance of the Copernican revolution, namely, the way Kant breaks with the tradition by considering how objects conform to the mind rather than the other way around. Kant states clearly that he learned from Galileo and the new sciences that ‘reason has insight only into what it itself produces according to its own design’ (Kant Reference Kant2000: Bxii–xiii). Rockmore thus concludes that although Kant’s language is inconsistent, constructivism is the more plausible interpretation on both philosophical and exegetical grounds. On his view, Kantian constructivism achieves the sought for identity of thought and being because the cognized object is always already formed by the subject. In other words, the subject knows only mind-dependent objects. Consequently, ‘in knowing, one knows oneself, or more precisely, oneself in the form of externality’ (35).

The response to the Kantian breakthrough was immediate and multifaceted. Rockmore begins with Reinhold’s attempt at formulating ‘a Cartesian foundationalist restatement of the critical philosophy’ (41). Reinhold, believing that Kant had shown that the ‘real foundation of philosophy is the fact of consciousness’, attempts to demonstrate that the true basic principle of critical philosophy is the ‘capacity for representation’ (49). Criticizing both Reinhold’s attempt to find an Archimedean point in the ‘law of consciousness’ and the central doctrines of Kant’s critical philosophy, Maimon adopts an anti-foundationalist stance: neither can we nor do we need to provide an ultimate justification for knowledge. The Erkenntnisproblem as formulated in Kant’s Herz letter is an insoluble red herring, distracting from genuine scientific inquiry into nature. The question of how we know what we know or how knowledge is possible is simply a non-starter, since all attempts to answer it prove to be hopelessly circular. Whereas, according to Rockmore, Maimon’s scepticism is informed by a nuanced reflection on the phenomena–noumena relation and an interpretation of the thing-in-itself, Schulze aims ‘merely to undermine any claim to establish certain principles’ (56). Nevertheless, Schulze clarifies an aspect of representationalism, namely that ‘claims to know require that the same representation relate to both subjective and objective epistemic poles’ (57).

The question of the relation of the subjective and objective poles in any cognitive activity lies at the heart of Fichte’s reformulation of Kant’s philosophy. On Kant’s account, the phenomenal object of knowledge is the product of an interaction between a mind-independent reality that cannot be known and the transcendental subject. According to Rockmore, Fichte’s attempt to improve on this view of cognition by making ‘the subject the sole explanatory factor’ comes at the price of ‘being unable to account for the objectivity of cognition’ (58). Thus, Fichte’s central thought in the Jena Wissenschaftslehre is ‘the claim that the subject depends only on itself’ (62). By ruling out the thing in itself or any mind independent source of cognition, the Kantian triadic relation constituting representation—‘the subject, the thing itself, and the empirical object given in experience and knowledge’—is reduced to the relation between object and subject. Fichte’s self-positing subject thus becomes ‘the source of all reality’ (69, 70). Accordingly, Fichte’s ‘Deduction of Representation’ attempts to establish ‘an identity in difference between subject and object, knower and known’ (73). Here, Rockmore evinces in spades one of the primary virtues of the book, presenting an extraordinarily condensed but lucid eleven-step summary of Fichte’s argument that the subject is self-determining.

Rockmore considers Schelling to undertake a partial return to Kant’s dualism ‘through the distinction between transcendental philosophy, which he takes over from Fichte, and philosophy of nature’ (81). In order to reconcile both perspectives, he is said to return ‘to a Spinozistic parallel between thought and being founded in a transcendent absolute’ (84). But how is this absolute to be known? Contra Kant’s denial of intellectual intuition, Schelling argues that ‘the subject intuits itself as productive’ (87). As Rockmore has it, Schelling’s constructivism turns on this ‘primordial mechanism of intuition itself’, since intuition itself is considered to constitute the object (87).

On Rockmore’s reading, Hegel is closer to Fichte than Schelling on key epistemic questions in the sense that he reformulates Fichte’s account of experience ‘from the perspective of the subject as an interaction between individuals and the world’ (92). Yet he ultimately differs from both Fichte and Kant by giving a deeply historical account of this interaction. After discussing Hegel’s early assessment of Fichte and Schelling, Rockmore turns to what he considers Hegel’s constructivist theory of knowledge in the Phenomenology. This theory rests on a twofold distinction between subject and object: (1) the subject distinguishes itself from something within consciousness, but in doing so also relates itself to that something, which it strives to cognize. (2) The subject distinguishes between what is ‘for it’ (given to consciousness) and what is ‘in itself’ (independent of the subject), which ‘would (if it were grasped) constitute the truth’ (107). This view of the subject-object relation is complemented by an understanding of the reciprocally co-determining nature of a concept and the object to which it corresponds. If a theory about the contents of experience changes, the object it is intended to comprehend also changes. In short, ‘the cognitive object is literally “constructed” by us in the process of knowing’ (108). Idealism makes this explicit in its claim that ‘reason … is itself all reality’ (109).

Hegel both builds on and surpasses Kantian philosophy by arguing that the understanding is a necessary stage but not ‘the terminus ad quem’ (152). In contrast to the limited cognition of the understanding, dialectical logic ‘results in an immanent linkage in creating a structured whole lying beyond its discrete parts, a whole that surpasses the finite’ (153). Hegel’s attempt to surpass Kant is likewise evident in his ‘general solution to the problem of the categories’ (156). Rather than deduce the categories as both Kant and Fichte attempt, Hegel illustrates how concepts ‘emerge in the effort to cognize conscious experience’ (166). Accordingly, Hegel’s constructivism is open-ended, proceeding through an a posteriori method in which concepts and theories of the world are subject to continual revision and adaptation.

Rockmore concludes with a survey of twentieth-century epistemological debates and the return of both foundationalism and scientific realism in Vienna Circle positivism. Although both epistemic projects have received sustained criticism from within the tradition of analytic philosophy, he claims that ‘the Parmenidean view that to know means to grasp the mind-independent real remains popular’ (171). On Rockmore’s telling, this metaphysical realism leads to failure and scepticism, as no one has ‘formulated a convincing argument to show that we can grasp the mind-independent real’ (171). The only feasible alternative he sees is a constructivism that ‘takes empirical realism as its cognitive standard’ (171).

According to Rockmore, we must also jettison the ‘normative conception of ahistorical knowledge’ (173) and acknowledge that any final, ultimate scientific theory can only be a regulative ideal. As he puts it, we have ‘no reason—none at all, since we cannot compare our theories of reality to reality—to think that we are almost there, or are even getting closer to grasping it’ (173). Rockmore reminds us that this position only appears as sceptical in light of an impossible standard—the result of ‘a longing for a halcyon ultimate resting place’ (173). His cognitive constructivism thus advocates that we pursue the effective truth as it is available to us rather than our imagined belief of how it ought to be. Historicism proves to be the corollary of constructivism.

As noted, Rockmore’s inquiry into German Idealism is situated within the broadest of frameworks ranging from Parmenides and Plato to twentieth century thinkers as various as Husserl, Quine and Rorty. The premise underlying this approach is that ‘there is more continuity than discontinuity between the ancient way of framing the cognitive problem … and modern efforts to resolve it’ (168). Although Rockmore’s central thesis does not hinge on this continuity, he seems to elide crucial differences between ancients and moderns, especially regarding constructivism in mathematics.Footnote ¹

In particular, the work of Jacob Klein and David Lachterman shows, contrary to Rockmore, how the constructivism of modern mathematics differs substantially from that found in Ancient Euclidean geometry (Klein Reference Klein1969; Lachterman Reference Lachterman1989). For Euclid, the intelligibility of the mathematical object lies in the eidos of the figure itself, but for Descartes intelligibility is a result of the geometer’s activity. Descartes’s emphasis on methodical constructivism as productive is not continuous with the Euclidean approach to geometrical construction, which is intended to exhibit the rational structure of the mathematical object, the ontological status of which is independent of the constructed instance. For Descartes, as long as the method is duly followed, the operation guarantees the validity of the construction. There is no criterion independent of the geometer’s operation that limits the kind or number of constructed objects and there is no independent standard of validity outside the necessity of the method. Whereas for Euclid construction was the exhibition of a truth about an object, for Descartes construction brings the object into being. This transformation, moreover, makes possible the new application of mathematics to nature that facilitates Descartes’ project of making man ‘master and possessor of nature’. In Descartes we see that modernity’s aim of mastering nature is connected with constructivism as a new cognitive procedure. As I see it, this transformation is crucial to understanding Kant’s appropriation of mathematics and the new science (Bacon and Galileo) as models for resolving the problem of cognition.

Rockmore’s insightful analysis of German Idealism as the continuous effort to perfect constructivism and thereby resolve the problem of cognition should prove useful to students looking for a guide to this complex set of figures and interesting to scholars debating the relevance of German Idealism to contemporary questions in metaphysics and epistemology. When viewed in light of the crucial mathematical, scientific and even political innovations of the sixteenth and seventeenth centuries, the work prompts this reader to consider the provocative possibility that constructivism, or the principle that ‘we know only what we make’, is the distinctive feature of modernity.