The Penumbra said to the Umbra, “At one moment you move: at another you are at rest. At one moment you sit down: at another you get up. Why this instability of purpose?”
“I depend,” replied the Umbra, “upon something which causes me to do as I do; and that something depends upon something else which causes it to do as it does. My dependence is like that of a snake's scales or a cicada's wings (which do not move of their own accord). How can I tell why I do one thing or do not do another?”