Addiction is almost universally held to centrally involve a loss of control over drug seeking and using. But there is a puzzle: Almost all the behavior involved in seeking and using drugs satisfies standard conditions for instrumental rationality and therefore seems to count as controlled behavior. I resolve the puzzle by arguing that addiction involves a loss of control not over behavior but over the states that control the behavior. Addicts experience cue-driven shifts in their mental states. I then turn to the implications of this account for moral responsibility. I argue that the disposition to experience such shifts entails an impairment of diachronic agency, and diachronic agency is a necessary condition of moral responsibility. There are therefore good grounds for excusing addicts for much of their behavior or at least significantly mitigating their degree of moral responsibility.
