Aristotle was active in the fourth century bce, so his thought is more ancient than that of any Christian philosopher. Aristotle's detailed and subtle conceptual scheme affords a range of notions that help us grapple with the phenomena of human wrongdoing. This chapter begins with Aristotle's notion of the 'mean', which is central to his account of vice. It analyses his conception of moral responsibility, which encompasses responsibility for both vicious action and vicious character. The chapter outlines Aristotle's metaphysics of vice, something unfortunately sidelined by much modern scholarship yet essential to understanding his overall moral theory. It unpacks his seemingly contradictory portrait of vicious character in Books VII and IX of the Nicomachean Ethics (NE). As Aristotle holds, the self-indulgent man is incurable, and the incontinent man curable; for wickedness is like a disease such as dropsy or consumption, while incontinence is like epilepsy; the former is a permanent, the latter an intermittent badness.