Necessarily, if S lacks the ability to exercise (some degree of) control, S is not an agent. If S is not an agent, S cannot act intentionally, responsibly, or rationally, nor can S possess or exercise free will. In spite of the obvious importance of control, however, no general account of control exists. In this paper I reflect on the nature of control itself. I develop accounts of control's exercise and control's possession that illuminate what it is for degrees of control-that is, the degree of control an agent possesses or exercises in a given circumstance-to vary. Finally, I demonstrate the usefulness of the account on offer by showing how it generates a solution to a long-standing problem for causalist theories of action, namely, the problem of deviant causation.