Whether people believe that they have control over their behaviors is an issue that is centrally involved in definitions of addiction. Our research demonstrates that believing in free will - that is, believing that one has control over one's actions - has societal implications. Experimentally weakening free will beliefs led to cheating, stealing, aggression, and reduced helping. Bolstering free will beliefs did not change participants' behavior relative to a baseline condition, suggesting that most of the time people possess a belief in free will. We encourage a view of addiction that allows people to sustain a belief in free will and to take responsibility for choices and actions.