Even if everything is up for grabs in philosophy, some things are very difficult to doubt. It is hard to believe, for example, that no one ever acts intentionally. Even the most powerful arguments for the unreality of intentional action could do no more, we believe, than place one in roughly the position in which pre-Aristotelian Greeks found themselves when presented with one of Zeno's arguments that nothing can move from any given point A to any other point B. One argument has it, for example, that in order to move from one point to another, a thing must first move to the half-way point; to do that, it must move half way to that point; and so on forever: so nothing ever moves at all. The argument undoubtedly stopped some auditors in their tracks; but eventually they moved on, most of them fully confident that they were doing precisely that.