REVERSAL OF CONTINGENCY INTO NECESSITY

The Penumbra asked the Shadow, saying, 'Formerly you were walking on, and now you have stopped; formerly you were sitting, and now you have risen up - how is it that you are so without stability?' The Shadow replied, 'I wait for the movements of something else to do what I do, and that something else on which I wait waits further on another to do as it does. My waiting, is it for the scales of a snake, or the wings of a cicada? How should I know why I do one thing, or do not do another? [Zhuangzi]