Book excerpt: Suppose that in an emergency evacuation of a hospital after a flood, not all of the patients can make it out alive. You are the doctor faced with the choice between abandoning these patients to die alone and in pain, or injecting them with a lethal dose of drugs, without consent, so that they die peacefully. Perhaps no one will be able to blame you whatever you decide, but, whichever action you choose, you will remain burdened by guilt. What happens, in cases like this, when, no matter what you do, you are destined for moral failure? What happens when there is no available means of doing the right thing? Human life is filled with such impossible moral decisions. These choices and case studies that demonstrate them form the focus of Lisa Tessman's arresting and provocative work. Many philosophers believe that there are simply no situations in which what you morally ought to do is something that you can't do, because they think that you can't be required to do something unless it's actually in your power to do it. Despite this, real life presents us daily with situations in which we feel that we have failed morally even when no right action would have been possible. Lisa Tessman boldly argues that sometimes we feel this way because we have encountered an 'impossible moral requirement.' Drawing on philosophy, empirical psychology, and evolutionary theory, When Doing the Right Thing Is Impossible explores how and why human beings have constructed moral requirements to be binding even when they are impossible to fulfill.