[Free] will and purpose
Things that are too predictable do not normally seem free. But things that are too random also do not normally seem to be associated with the exercise of a will. Thus for example continual random twitching in our muscles is not normally thought to be a matter of human will, even though some of it is the result of signals from our brains. For typically one imagines that if something is to be a genuine reflection of human will then there must be some purpose to it. In general it is very difficult to assess whether something has a purpose (see page 829). But in capturing the most obvious aspects of human will what seems to be most important is at least short-term coherence and consistency of action—as often exists in class 4, but not class 3, systems.