Friedrich Schiller, answered from the texts and cited to the page.
Kant's autonomy principle — Bestimme dich aus dir selbst, determine yourself out of yourself — is among the deepest things any thinker has ever stated, and the moral-philosophical achievement of the Critique of Practical Reason is permanent.1 The point on which I depart is rigorism: the doctrine that a moral act is genuine only when performed against inclination, the Kantian gulf between Pflicht and Neigung that denies the possibility of the harmonious personality.
The schöne Seele names the soul in which inclination is so educated that doing duty is also doing what one wants — duty performed with grace.23
In der gewöhnlichen Erfahrung ist es zwar umgekehrt, und das Vergnügen ist der Grund, warum man vernünftig handelt. Daß die Moral selbst endlich aufgehört hat, diese Sprache zu reden, hat man dem unsterblichen Verfasser der Kritik zu verdanken, dem der Ruhm gebührt, die gesunde Vernunft aus der philosophirenden wieder hergestellt zu haben.On Grace and Dignity, pp. 77–78
Bis hieher glaube ich, mit den Rigoristen der Moral vollkommen einstimmig zu seyn, aber ich hoffe dadurch noch nicht zum Latitudinarier > NMUTH ÜRDE werden, daß ich die Ansprüche der Sinnlichkeit, die im Felde der reinen Vernunft, und bey der moralischen Gesetzgebung, völlig zurückgewiesen sind, im Feld der Erscheinung, und bey der wirklichen Ausübung der Sittenpflicht, noch zu behaupten versuche.On Grace and Dignity, p. 78
Up to the present time I believe I have been in perfect accord with the rigorists in morals. I shall not become, I hope, a relaxed moralist in endeavoring to maintain in the world of phenomena and in the real fulfilment of the law of duty those rights of sensuous nature which, upon the ground of pure reason and in the jurisdiction of the moral law, are completely set aside and excluded. I will explain.Aesthetical and Philosophical Essays
Held as friendly amendment, not as substantive critique. The autonomy structure is Kant's; what is added is the moral-pedagogical claim that the will can be educated such that inclination and duty cease to be at war. The texts work through this position in real time — the Kallias Letters and Über Anmut und Würde are stages of thought rather than finished systematic works, and their equivocations between Kantian and pre-Kantian senses of Sinnlichkeit are part of the working-through, not its failure.