How Moral Psychology Can Help Us Understand Deep Contestation of the Prohibition on the Threat and Use of Force

Abstract This chapter explores one of the most important deep contestations of the liberal international order (LIO): the contestation on the prohibition of the threat and use of force against the territorial integrity or political independence of any state. The focus is on great power breaches of the prohibition of the threat and use of force, particularly the Russian invasion of Ukraine in 2023, the US invasion of Iraq in 2003, and Trump’s 2025 threats to invade Greenland and Panama. Understanding such deep contestation requires political science to move beyond its overly rationalist mode. These cases illuminate the need to better incorporate intuition- and emotion-fueled morality into our understanding of politics. This chapter suggests explanations for deep contestation using the moral foundations literature in psychology and argues that such contestation comes to the fore today because of some of the dramatic changes produced by the “successes” and “excesses” of the liberal order.