Adolf says
Quite. I have tested myself. When I went to bed the evening after our conversation I reviewed your chain of argument point point, and felt convinced that it was sound. But the next morning, when my head cleared again, after the night’s sleep, the thought flashed through me like lightning that you might be mistaken all the same. I jumped up, and snatched up a brush and palette, in order to paint, but -just think of it! -it was all up. I was no longer capable of any illusion. The whole thing was nothing but blobs of color, and I was horrified at the thought. I could never have believed I could convert any one else to the belief that painted canvas was anything else except painted canvas. The scales had fallen from my eyes, and I could as much paint again as I could become a child again.