Chapter 5 : Touch and Sight

Twist the index finger with the middle finger and place between these fingers intertwined a small ball in such a way that it touches both, and then shut your eyes. It will seem to you that you are holding two balls. Open your eyes and you will see that it is only one. Your fingers have deceived you, and your eyes have corrected the impression.

Look best of all a little sidewise at a good, clear mirror, it will seem to you that it is a window or a door, and that there is something behind it. Touch it with your fingers and you will assure yourself that it is a mirror. Your eyes deceived you, but your fingers cor- rected the impression.