Morality Games 299 Why don’t we consider it murder to let someone die that we could have easily saved? For example, we sometimes treat ourselves to a nice meal at a fancy restau- rant rather than donating the cost of that meal to a charity that fights deadly diseases. This extreme example illustrates a general phenomenon: that people have a ten- dency to assess harmful commissions (actions such as killing someone) as worse, or more morally reprehensible, than equally harmful omissions (inactions such as let- ting someone die). Examples of this distinction abound, in ethics (we assess with- holding the truth as less wrong than lying (Spranca, Minsk, & Baron, 1991)), in law (it is legal to turn off a patient’s life support and let the patient die, as long as one has the consent of the patient’s family; however, it is illegal to assist the patient in committing suicide even with the family’s consent), and in international relations. For example, consider the Struma, a boat carrying Jewish refugees fleeing Nazi persecution in 1942. En route to Palestine, the ship’s engine failed, and it was towed to a nearby port in Turkey. At the behest of the British authorities then in control of Palestine, passengers were denied permission to disembark and find their way to Palestine by land. For weeks, the ship sat at port. Passengers were brought only minimal supplies, and their requests for safe haven were repeatedly denied by the British and others. Finally, the ship was towed to known hostile waters in the Black Sea, where it was torpedoed by a Russian submarine almost immediately, killing 791 of 792 passengers. Crucially, though, the British did not torpedo the ship them- selves or otherwise execute passengers—an act of commission that they and their superiors would undoubtedly have found morally reprehensible. Why do we distinguish between transgressions of omission and commission? To address this question, we present a simple game theory model based on the insight by DeSci