Reasons and obligations pervade our lives. The alarm clock gives us a reason to get up in the morning, the expectations of colleagues or clients give us a reason to do our jobs well, the misery in developing countries gives us a reason to donate money to Oxfam, a headache gives us a reason to take an aspirin. Looking for unity in variety, philosophers wonder why a consideration counts as a reason to do something. The nature and source of practical reasons have been debated intensively over the last three decades in analytical philosophy. This book discusses the three most influential theories