It is widely held that in Plato's Sophist, Forms rest or change or both. The received opinion is, however, false—or so I will argue. There is no direct support for it in the text and several passages tell against it. I will further argue that, contrary to the view of some scholars, Plato did not in this dialogue advocate a kind of change recognizable as 'Cambridge change', as applicable to his Forms. The reason that Forms neither change nor rest is (...) that they are purely intelligible entities, not susceptible to changing or being at rest. Since Plato continues in the Sophist to treat Forms as causes, it follows that Forms are changeless causes. I ask what conception of cause might allow for this view, and reject the suggestion that Plato was some kind of proto-dispositionalist about causation. Instead I suggest that he understood causation to incorporate a notion of structuring, such that Forms can be seen to structure their participants and so cause them to possess the attributes they possess. (shrink)