As a Lutheran teacher and writer on philosophical and theological topics, Johann Gottlieb Rätze (1760–1839) was typical of the first generation of Kant disciples. Rätze initially had doubts about Kant’s moral philosophy. He had baulked at the hurdle that sent many potential converts tumbling back into Christianity: namely, Kant’s teaching that the will of sensuous beings could be governed through a philosophical idea of the moral law, in the absence of divine command and without the reward of divine beatitude promised by Christianity. What converted Rätze to Kantianism was his sudden insight, obtained through the reading of Kant’s Religion Within the Boundaries of Mere Reason, that Kant’s philosophy could provide the same kind of spiritual transformation and elevation as religion.
In 1794 Rätze recorded his conversion in the following terms:
But through Religion Within the Boundaries of Mere Reason, my respect for the author involuntarily rose to the highest level. I saw and felt that the author of this work was one of the greatest religious teach-ers. [. . .] Should someone ask, Why do I call Kant a religious teacher and not just a philosopher? [. . .] I would say, That’s precisely why he is a great philosopher, because he is a great religious teacher. From now on, the true philosopher will or at least should be the best religious teacher, and religion and everything that is sacred to humanity has nothing to fear from him, but everything good to hope for.
Rätze went on to provide the following characterisation of the religion that Kant was teaching:
The pure moral religion [reine moralische Religion] is and remains good without any restrictions. It is and remains everywhere beyond all disputation. Whether it appears in a sensory garment or without one, whether it comes from mere reason or from the mouth of a super-natural messenger, in either case it remains above all worthy of rever-ence. Whether one regards her as the immediate daughter of heaven or of reason, she walks in heavenly splendour and inexpressible beauty.
Finally, this pious Lutheran Kantian concludes with a powerful evocation of the way in which Kantian philosophical reason was assuming the tasks of illumination and regeneration previously fulfilled by Christian teaching. If this meant that Kantian philosophy was inheriting Christian sublimity, then it was simultaneously supplying the latter with a rational ground:
The salvation that the genuine doctrine of Christ intends is also what the moral philosopher means, and no other. Pure practical reason as such is just as divinely disposed as all things that have descended from heaven in an extraordinary way. What no eye sees in the world of sense [Sinnen-welt], what no inclination desires, she [pure practical reason] recognises through her heavenly light, and wills with her impeccable will. The sub-lime objects that she contemplates and firmly wills are God, immortality and virtue. Even if we suppose that reason owes its perfect insight into the divine and invisible goods to a special teaching sent down directly from heaven, it must have had within itself beforehand an a priori capacity to determine the form and matter of an extraordinary revelation to be able to recognise and accept it as divine.
Here, we can see a full symptomatic expression of the way in which Kantian philosophy had moved into the cultural space that had been previously domi-nated by ecclesial Christianity. True to Kant’s basic teachings, Rätze declares that philosophical reason itself now provides access to sublime objects that had been the preserve of the Christian religion: to the invisible world lying beneath or above the world of sense, and to the impeccable purity of a will grounded in reason to the exclusion of all sensuous desires. In providing an extra-ecclesial path to these sublime objects, Kantian philosophy should itself be regarded as divinely disposed and heaven-sent and thence as harmoniouswith Christ’s teaching. At the same time, Rätze leaves his readers in no doubt that, rather than Christ, it is philosophical reason that is the ultimate source of holiness. That is because it is reason that provides the a priori criteria for recognising Christ’s own divinity, which will itself turn out to be philosophical.
Rätze’s view of the sublimely religious character of Kantian philosophy and of Kant himself was anything but eccentric. In the emotional intensity with which he superimposed philosophical regeneration on Christian salvation, in the audacity with which he treated Kantian reason as the criterion for recognising the divinity of Christianity and in the fundamental figure of thought in which he separated sensible knowledge of the “world of sense” from the supra-sensible or a priori insight of pure practical reason, we will see that Rätze was unfailingly representative of Kant’s early followers. That Kantian philosophy was understood to be a kind of religion by its enemies no less than its friends can be seen in works by those for whom “philosophical religion” was a pejorative. For these anti-Kantians, philosophical religion signified a philosophy that was attempting to supplant Trinitarian confessional Christianity by a philosophical doctrine that falsely claimed to be the true meaning of Christianity and to possess the power of moral regeneration.
Excerpted from The Kantian Religion by Ian Hunter, published by Princeton University Press, ©2026 by Ian Hunter. All Rights Reserved.
