How does war influence moral judgments about harm? While the general rule is "thou shalt not kill," war appears to provide an exception to the moral prohibition on intentional harm. In three studies (N = 263, N = 557, N = 793), we quantify the difference in moral judgments across peace and war contexts, and explore two possible explanations for the difference. The findings demonstrate that people judge a trade-off of one life for five as more morally acceptable in war than in peace, especially if the one person is from an outgroup of the person making the trade-off. In addition, the robust difference in moral judgments across "switch" and "footbridge" trolley problems is attenuated in war compared to in peace. The present studies have implications for moral psychology researchers who use war-based scenarios to study broader cognitive or affective processes. If the war context changes judgments of moral scenarios by triggering group-based reasoning or altering the perceived structure of the moral event, using such scenarios to make decontextualized claims about moral judgment may not be warranted.
Key words: moral psychology, trolley problems, war, ingroup bias, intergroup conflict THE INFLUENCE OF WAR ON MORAL JUDGMENTS 3 The Influence of War on Moral Judgments about HarmKilling is wrong; therefore all murderers are punished unless they kill in large numbers and to the sound of trumpets.
-VoltaireThe moral judgments we make about killing in war differ markedly from the moral judgments we make about killing in times of peace. In an everyday context, the quintessential moral wrong is intentional harm (i.e., murder, Gray & Keeney, 2015), and the most common immoral actions observed in people's everyday lives involve harm (Hofmann, Wisneski, Brandt, & Skitka, 2014). But what about in contexts of war? Although harm is highly relevant in war contexts -in the 20 th century, upwards of 110 million people lost their lives in international and civil wars (Wimmer, 2014) -very little research compares judgments of harm in war to judgments of harm in everyday contexts. Thus, while it is generally assumed that harm is more permissible in war than in peace, this difference in moral judgments has yet to be quantified. In addition, no previous research has investigated how war influences moral judgments. Is it the "large numbers", or "the sound of trumpets" that is driving the effect? Or something else entirely?In the present paper we compare judgments made about harm in a peace context to those made in a war context, to investigate how war influences moral judgments. We also investigate two specific aspects of the war context which may underpin any observed difference: (a) the intergroup nature of war, and (b) the context-specific nature of the construal of causal and intentional event structure. We aim to further our understanding of moral judgments about actions in war -particularly about its core activity, killing. Philosophers of (the ethics of) war have suggested that how we make moral judgments about killing in wa...