A partially completed drawing by Goethe included in his 1790 “Zur Morphologie”
"They arrive at Schiller's house and, still talking, Goethe enters. This is Goethe's account of the occasion: 'I explained to him with great vivacity the Metamorphosis of Plants and, with a few characteristic strokes of the pen, conjured up before his eyes a symbolical plant. He listened, and looked at it all with great interest and intelligence; but when I had ended, he shook his head saying: This has nothing to do with experience, it is an idea. I raised my eyebrows, somewhat annoyed. For he had put his finger on precisely the point which separated us. His argument from Anmut und Würde came to my mind; the old anger began to stir, but I constrained myself and replied: Well, so much the better; it means that I have ideas without knowing it, and can even see them with my eyes.' They carried on their discussion with great polemical obstinacy on each side. Goethe reports that some of Schiller's sentences made him 'quite unhappy'; for instance, the following: 'How can one ever equate experience with ideas? For an idea is characterized precisely by the fact that experience can never be fully congruous to it.' And, Goethe, in his account of the discussion, reflects that 'if he takes for an idea what for me is experience, then there must, after all, prevail some mediation, some relationship between the two'.
From The Disinherited Mind: Essays in Modern German Literature and Thought by Eric Heller.