In this parable, the water is not conscious of the causal setups necessary for it to boil, make waves, and so on. It only remembers that it sometimes does these things. Hence, it thinks, it can do them. So it attributes its calm to its own voluntary decision. But in this it is mistaken: if it ‘tries’ to boil when the temperature is wrong, or ‘tries’ to make waves when there is no wind, it will soon discover that these things do not depend on its own decision.
