I don't see the 'of course' at all. If you once praise a picture, your character for infallibility hangs by a thread. Somebody measures it, and finds one of the proportions an eighth of an inch wrong. From your point of view, that is correctly put. But for anyone who has a soul for Art, such a view is preposterous.
Nature is one thing.
Art is another. Nature shows us the world as it is. And, for a few peaceful moments, the orator brooded, frowningly, over the quotation. The welcome opportunity was seized, and another voice struck into the silence. Arthur slightly smiled.