The decline of Naturphilosophie deeply polarized the philosophical and scientific debate. Naturalistic–materialistic positions gained powerful influence, but the latent role of the Kantian critical position also re-emerged in the context of an “ideal-realism”. I will first consider in detail two opposing treatments of Kant’s perspective. After Lotze had criticized his earlier materialistic position, advising him to read Kant, Czolbe finally addressed Kant, thereby progressing to a non-materialistic form of naturalism. However, whether to defend or to dismiss naturalism, neither philosopher addresses (...) Kant as a transcendentalist thinker, and I go on to examine this common feature in their writings. This invites us to reconsider what exactly in Kant’s system conflicts with naturalism. Is transcendentalism too broad a requisite for that task? Within “ideal-realism”, the realist part actually implies a denial of transcendental idealism; still, it shows how a realism which refuses to be naturalism could well learn from Kant. (shrink)