 From at least Aristotle onwards, ancient philosophers engaged in systematic reflection on human agency. They asked questions about when people are morally responsible for their actions and what must be the case for people to deliberate and act effectively, and in doing so they confronted arguments that tried to establish that humans are not responsible and effective agents. But if we want to understand these philosophers correctly, we should be careful not to assimilate ancient theories of freedom and determinism too quickly to the problem of free will and determinism in contemporary philosophy, which asks whether causal determinism is compatible with the sort of freedom—or alternatively, with the sort of control over our actions—that is necessary for moral responsibility. (See the entries on  free will  and  causal determinism.)  While ancient philosophers did argue about whether causal determinism is compatible with moral responsibility, their concerns ranged more widely. We can divide their discussions into two broad areas.