Walter Jaeschke’s Reason in Religion: The Foundations of Hegel’s Philosophy of Religion stakes a precise claim: it reconstructs, with philological rigor and systematic intent, how Hegel regrounds the very possibility of a philosophy of religion by reopening the question that Kant appeared to close—whether speculative reason can know God—and by tracking how that reopening reshapes the inner architecture of Hegel’s system from Jena through Berlin. The book’s distinctive contribution lies in its double movement: first, a historical-critical demonstration that Kant’s moral recuperation of theology is methodologically unstable; second, a systematic exposition of Hegel’s speculative alternative as it crystallizes across genres (logic, phenomenology, encyclopedia, lectures), culminating in a developmental interpretation of the Berlin Lectures on the Philosophy of Religion made possible by the newly reconstructed text Jaeschke himself edited.
Jaeschke frames the entire undertaking by restoring the unity of a question that nineteenth-century divisions had obscured: the philosophy of religion cannot be kept safely apart from philosophical theology without quietly shifting its object from God to human religious behavior. If philosophy of religion treats religion merely as a phenomenon and brackets the question of God, it cedes the very point of religion to anthropology; yet if it presupposes a theological ground it has not philosophically justified, it abandons its vocation. Hence the problem that governs the book’s introduction: can a philosophy of religion be both philosophically autonomous and adequate to religion’s own claim that it concerns a reality irreducible to human projection? The introduction names that dilemma with exemplary clarity and insists that answering it requires revisiting Kant’s interdiction of speculative theology and his practical turn. The core methodological thesis emerges here: unless some form of philosophical theology is possible, the philosophy of religion can only be an anthropology of religious expressions, regardless of whether its rhetoric is pious or critical.
The outer architecture follows from this problem-setting. Four studies are interlinked but distinct: a reconstruction of the late-Enlightenment scene and the Kantian settlement; an analysis of the Jena writings as the speculative foundation; a developmental reading of the Berlin lectures on religion; and an account of the posthumous controversy that exposes fault-lines in reception and in Hegel’s own architectonics. This fourfold composition is not arbitrary editorial convenience, it enacts Jaeschke’s conviction that one must go “behind and beyond” the most mature exposition if one is to clarify both the grounds and the stakes of Hegel’s speculative enterprise. The preface explicitly avows this strategy and identifies the edition of the Berlin lectures (edited by Jaeschke) as the textual hinge that allows a developmental interpretation of Hegel’s mature position.
Jaeschke’s point of departure is Kant—not as a straw man but as the unavoidable watershed for any modern theology or anti-theology. The first study parses the Kantian triple: the critique of speculative proofs, the practical restitution of the idea of God, and the redefinition of religion as moral reason’s relation to a sovereign lawgiver. The argumentative structure matters. Kant’s refutation of speculative theology reaches its decisive pressure-point in the ontological proof’s misconstrual of the relation between concept and being; yet, as Jaeschke stresses, the deeper nerve of the Kantian veto lies in the claim that even if a non-contradictory concept of a necessary being is thinkable, the theoretical route has no right to hypostatize it. That criticist move blocks the very grammar of a “most real being” and simultaneously narrows the space religion may legitimately occupy within philosophy. The result is a forced migration: theology must move into practical reason, where God becomes the condition for the highest good and where religion is defined as the knowledge of duties as divine commands.
But that migration, Jaeschke argues, is not doctrinal consolidation—it is a tension-engine. The “ethical theology” that Kant advances is built from several strands produced at different stages of his practical philosophy; as a result, its unity is more asserted than won. The consequence is internal strain between the autonomy of ethics and the subordination of ethics to a theological postulate. If the moral law binds unconditionally by reason alone, the idea of God cannot be its ground without imperiling autonomy; if, however, the moral end (the highest good) requires God as a guarantor of the proportionality of virtue and happiness, then ethics leans on what it can neither know nor deduce. In Jaeschke’s reading, Kant’s project burdens practical reason with a theological weight it cannot carry, thereby generating a series of compensations—tightening the definition of religion as “morality in relation to God as lawgiver,” policing speculative theologoumena as corrupting imports, and moving the decisive function of God to the realm of hope. Taken together, these compensations illuminate the unsatisfactory nature of the practical restitution: it neither secures theology philosophically nor preserves the purity of ethics without remainder.
At precisely this juncture Jaeschke shows how Hegel’s project becomes legible—not as a nostalgic return to pre-critical metaphysics, but as an attempt to rethink, from within logic, the very terms that made Kant’s interdiction compelling. Hegel’s strategy—and Jaeschke’s insistence on reading it as a strategy rather than as a set of dogmas—is to transform the conceptual field on which “concept” and “being” are opposed, and to re-articulate “necessity,” “reality,” and “idea” such that the very grammar of “an ens” becomes inadequate to the absolute. The Science of Logic is thus not merely a prolegomenon; it is a rehabilitation of metaphysics that refuses to resume the old favors and instead reframes the ontological question as a question internal to the movement of the concept. Hegel’s response to Kant, on Jaeschke’s account, is neither to deny the criticist objections nor to replay the classical proofs, but to show that the unity of thought and being is not an extrinsic add-on to a concept of God; it is the very form of the absolute idea. The point for the philosophy of religion is methodological: if this transformation holds in logic, then a philosophical theology can be articulated without falling back into the hypostatizations Kant rightly exposed.
The Jena materials—sermons, system sketches, early essays, and fragments—receive in Jaeschke the status they deserve: they are the crucible in which Hegel first figures a speculative science of the idea that can bear the philosophy of religion. Here one sees Hegel both wrestling with the immediate post-Kantian alternatives (ethical theology, anthropological reduction, prophetic immediacy) and experimenting with placements of religion alongside aesthetics and ethical life. The thesis that emerges is precise: a philosophy of religion becomes systematically possible only to the extent that speculative philosophy has shown the possibility of metaphysical knowledge and has justified within itself the transition from concept to the actuality that conceptually belongs to spirit. Otherwise one ends with “a merely presumptive science of what people call ‘the human being.’” The Jena period accordingly builds the conditions for a later, determinate form of the discipline by exhibiting, in nuce, philosophy of religion as science of the idea, as aesthetics, as philosophy of ethical life, and (finally) as a moment within the Phenomenology. The lines do not run in parallel; they cross and displace.
Methodologically, Jaeschke’s emphasis on Jena does two things. It shows first that Hegel’s religionsphilosophische claims never hang in the air; they are tethered to a critique of Kant and Jacobi’s anti-metaphysical strictures and to a constructive proof of metaphysics as science. Second, it shows how Hegel’s speculative christology—already in Frankfurt and Jena—presses an ontological thesis that refuses the violent separation of finite and infinite. The principle is crystalline in Jaeschke’s reconstruction: where divine and human nature are severed, the “positive” hardens into mere positivity; reconciliation requires the thought of unity, and that thought is not a lyrical flourish but a metaphysical claim. The early reflection that “there are not two independent wills, two substances; God and humanity must therefore be one” is not a naïve Spinozism; it is a signal that christology and ontology will be articulated together when the system matures.
With the conceptual base in view, Jaeschke turns to the centerpiece: the Berlin Lectures on the Philosophy of Religion. The critical edition allows him to do what earlier editors obscured: trace real development. The invariants matter: every cycle is structured in three parts—concept of religion; determinate religion (history and typology); consummate religion (Christianity). Yet the invariants are not self-explaining; Hegel’s own gloss that “scientific knowledge” tends to move from concept to particularization to self-return is not, Jaeschke argues, a sufficient justification, especially since no other major discipline maps itself exactly this way. The tripartition is thus both fitting (given the nature of spirit) and methodologically opaque; it requires a justification Hegel never fully provides in lecture form. The developmental reading then earns its keep: the place of the “Concept of Religion” and the separation of “Consummate Religion” from the historical series reflect a deliberate shift away from the Phenomenology’s treatment, where no separate concept is first fixed. This shift signals a change in how Hegel thinks the relation between the universal concept and its historical embodiments—one now mediated by an explicit conceptual prolegomenon that can measure history without dissolving it into logic.
Jaeschke draws out the further implication: if the concept of spirit explains why a discipline might move from concept to historical realization to consummation, it also raises a structural question that Hegel leaves unanswered—why does philosophy of religion (and not, say, right or art) adopt precisely this sequence? The answer cannot be a facile appeal to triads; it must be specific to the way spirit is present to itself in religion. Jaeschke’s sober verdict is that, with the sources we have, we cannot derive a uniform architectonic across the system; correspondences can be noted but not grounded, and attempts to align the logic of the lectures point-by-point with logical forms of judgment or inference are misconceived. The philosophical gain here is negative but illuminating: development in the lectures is real, tied neither slavishly to the Logic nor arbitrary, and the discipline’s form is constrained by its object—spirit relating to itself in the medium of representation.
This emphasis on representation is decisive in Jaeschke’s analysis of the third part (“consummate religion”). Hegel there articulates a speculative theology, a speculative christology, and a speculative pneumatology: the Idea in the element of thought; the same Idea in the element of representation; and the same Idea as self-conscious community and cultus. Jaeschke is not content to paraphrase; he tests the internal consistency of the passages where representational form and conceptual content are most exposed to one another. Critique that targets representational deviations from doctrinal orthodoxy has limited force, he argues, unless it can show a conceptual inconsistency. Conversely, where Hegel’s conceptual articulation presses the representational forms, the pressure is not a failure of piety but the philosophical necessity of translation between elements—Begriff and Vorstellung. The weight of Jaeschke’s claim is that the lectures recognize this translation task explicitly; they acknowledge the theologian’s concern but set the stakes where they belong for philosophy: the consistency of the concept as it is exhibited through religious representation.
If the Berlin exposition is the architectonic center, the controversy that followed Hegel’s death is its diagnostic afterlife. Jaeschke’s narrative here is neither apologetic nor polemical; it is analytic. By rehearsing the debates over the personality of God and the immortality of the soul, he shows how the reception forced to the surface tensions that the lectures contain. The criterion of “Christian character” often came to mean conformity to the uncriticized intuitions of a “pious heart,” which judged philosophy’s adequacy by devotion’s temperature. Against that measure Hegel is destined to fail, not because philosophy is anti-religious, but because speculative argument dissolves ungrounded oppositions (transcendence/immanence, personality/substance, finitude/infinitude) and cannot reproduce devotional immediacy. Here Jaeschke reads the thirty-year debate with a steady hand: the left and right Hegelians alike often mislocate the question, oscillating between a logicized God without life and a warmed-over orthodoxy without concept; the real issue is whether a concept of absolute subjectivity is philosophically articulable as the truth of the religious representation of divine personality, and how that concept relates to the logical absolute idea.
Several of Jaeschke’s claims sharpen precisely at this interface of logic and religion. First, religion is rebedded within a metaphysical system without becoming logic’s annex. The lectures do not reduce religion to the Logic, nor do they weave a “ragged patchwork” of metaphysics and morals; rather, they position religion in its constitutive relations to art, ethical life, and absolute knowing while preserving its integrity as spirit’s necessary mode of self-relation in the element of representation. This prevents the slide into either aestheticization (religion as poetic surplus) or moralization (religion as ethical pedagogy). Second, the very possibility of a philosophy of religion—which Kant appeared to secure only at the cost of reducing religion to ethics—returns once metaphysics as science is rethought. The point is not to import dogma into philosophy; the point is to exhibit, within philosophical exposition, why and how the idea of God is both conceivable and in some sense unavoidable for thought that would be adequate to its object.
The result is a book resolutely problem-laden by design. Each advance folds back a question. Kant’s practical turn promises to save religion for philosophy; Jaeschke shows the price is the quiet emptying of theology into a postulate whose content cannot be known and whose function destabilizes the autonomy it was meant to preserve. The Jena foundation promises speculative solidity; Jaeschke shows that the very success of logic’s rehabilitation forces fresh questions about the translation of concept into representation and about the rightful form of a discipline whose object is spirit’s self-relation. The Berlin lectures promise architectonic closure; Jaeschke shows that the invariant tripartition sits atop unresolved tensions about justification of form, distribution of topics, and the relation of doctrine to concept. The posthumous controversy promises clarity through opposition; Jaeschke shows that polemics often obscure the central issue—how to think divine personality as absolute subjectivity without collapsing God into either a bare logical process or a merely human projection.
An especially instructive constellation is Jaeschke’s treatment of the Kantian definition of religion as “morality in relation to God as lawgiver.” On its face this renders theology instrumentally “useful to religion”; in substance it effaces the distinction between a theology that grounds religion and the moral law that would ground itself. The very act of preserving moral purity by removing speculative content thus depends on an identification that makes religion indistinguishable from ethical theory unless content is restored; yet any restoration on speculative grounds would, from the Kantian standpoint, threaten the moral core with heteronomy. Jaeschke’s diagnosis is crisp: this is a circle, and it explains why the practical restitution of theology oscillates between marginalizing God and making God indispensable to a highest good whose content remains problematic. The counter-movement in Hegel is therefore not an additive “doctrine of God” but a reconfiguration of the loci in which theology and religion meet: concept, representation, community.
One can see Jaeschke practicing what he ascribes to Hegel. The opening historical-critical study destabilizes the Kantian settlement and issues in a need for a speculative foundation; the Jena study fulfills that need but cannot yet determine the discipline’s final shape; the Berlin study supplies the shape and exhibits pressures in its own edifice; the controversy study both concludes the arc and discloses where the work’s concepts, once public, will necessarily be tried against rival measures (doctrinal conformity, devotional immediacy, speculative consistency), thereby refracting back into the earlier studies new questions about method and form. The sequence is not merely chronological; it is architectonic, since each part presupposes and transforms the prior.
The compositional discipline bears fruit in two particularly valuable clarifications. First, on method: Hegel’s steady refusal to offer a prior external proof of the possibility of philosophical theology is neither obscurantism nor dogmatic bravado. It follows from the requirement that proof be immanent to exposition; whether speculative theology is possible can only be decided in the act of philosophizing. Jaeschke brings out how this self-binding distinguishes Hegel’s response to Kant from any simple restoration of the pre-critical proofs. Second, on the function of the history of religion: Hegel’s infrastructure of “determinate religion” is neither an empirical anthology nor a crypto-evolutionism but the medium in which the concept’s necessity is realized and measured. The separation of “consummate religion” from the historical series is therefore more than didactic; it registers that Christianity, as the representation most adequate to the concept, must be treated as the site where concept and representation most nearly coincide, without erasing the representational character that keeps philosophy and religion distinct elements.
A final set of tensions shows why Jaeschke’s book matters for present philosophical theology. If speculative philosophy exhibits God as absolute idea and absolute spirit, how can it also do justice to the personality to which religious consciousness prays? If the “immortality of the soul” is in religion a figurative representation of spirit’s infinitude, what is lost and what is gained when the figure is translated into concept? If the logical identity of thought and being is the necessary horizon of speculative theology, how does one prevent “God” from dissolving into a process-name for the concept’s self-movement? Jaeschke does not resolve these questions by fiat. He shows that Hegel’s own expositions acknowledge their pressure and that the controversy proves such pressure intrinsic to the project, not a mistake to be tidied away. It is because these tensions are constitutive that Jaeschke’s insistence on the conceptual primacy of philosophical exposition over representational policing is salutary: without the concept’s inner articulation, appeals to orthodoxy are empty; without the discipline of representation, concepts forget the element in which religion actually lives.
Hegel’s philosophy of religion, as reconstructed by Jaeschke, neither evacuates transcendence into moral feeling nor freezes it into a transcendent ens set over against the finite. It articulates transcendence as the self-relation of spirit where concept and representation, universality and historicity, freedom and necessity, are held together—aliquid per aliquid, but within the immanence of thought’s truth-relation to being. That attempt will always provoke the twin accusations that have shadowed it since the 1830s: that it is too logical to be religious, and too religious to be philosophical. Jaeschke’s book shows why yielding to either accusation would be a failure of nerve about philosophy’s vocation. If philosophy of religion is to be more than anthropology and more than dogmatics, it must risk speculative theology—and thus risk the very questions this book teaches us how to ask well.
In that sense Reason in Religion is not only a major contribution to Hegel scholarship; it is a methodological intervention in contemporary philosophy of religion. Its wager is that the idea of God is philosophically conceivable and in a precise sense unavoidable once the conditions of speculative thinking are restored; its demonstration is to show, text by text and structure by structure, how Hegel makes that wager thinkable without confiscating religion into either morality or poetry. The result is a work in which historical exegesis and systematic ambition converge—each correcting the other, each generating pressures that the other must absorb—and in which the old question, whether philosophy can know God, is posed again with a seriousness proportionate to its difficulty.
The book’s scholarship supports a simple claim with complex consequences. Philosophy of religion requires philosophical theology if it is to speak of God and not merely of us; speculative theology requires a rehabilitated metaphysics; a rehabilitated metaphysics requires that Kant’s interdiction be both acknowledged and surpassed; and that surpassing, once achieved, changes how the history, concept, and consummation of religion must be presented. Jaeschke neither softens nor sensationalizes that chain. He explicates it patiently—through Kant’s limits, Hegel’s reconstruction, the lectures’ form, and the controversy’s tests—so that readers can see how the parts interpenetrate, displace, and finally illuminate one another in the element of reason itself.
Simon Gros 
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