Our central question has been, how far and in what ways does (and should) the world impinge upon us as we attempt to live in a valuable way? How far are we creatures who, like plants, depend passively upon what is outside of us in the world of nature? How far are we purely active intellectual beings like the souls of Plato's middle dialogues? And what is, for a human being, the best (most praiseworthy) way to be? One of the things such questioning demands is, clearly, an account of human action. We need to consider how our various movements in the world are caused, if we are going to be able to say what sorts of causal relationships between world and agent diminish, or remove, the praiseworthiness of a life. Plato's thought about ethical self-sufficiency has relied implicitly on a picture of action. In the middle dialogues we are presented with a double story. On the one hand, there is the self-moving, purely active, self-sufficient intellect, generator of valuable acts; on the other, there are the bodily appetites, which are themselves passive and entirely unselective, simply pushed into existence by the world and pushing, in turn, the passive agent.