This book brings together papers by a set of thinkers united in their belief that understanding agency - and failures of agency - requires engagement with the best contemporary science. The eleven papers included attempt to illuminate the mechanisms involved in addiction. They address the ways and degrees to which addiction-driven actions are controlled by the agent. They explore the extent to which such actions express the values of the agent, and the extent to which addicts are responsible for what they do. Some of the papers focus on the neuropsychological mechanisms involved, especially on the role of the midbrain dopamine system. Others focus on features of the behavior and the extent to which we can infer psychological mechanisms from behavior. The authors debate the best interpretation of the scientific evidence as well as the extent to which scientific evidence bears upon, or can only be understand in the light of, philosophical theorizing about agency, control and responsibility.