International audience In many cultures oaths, ordeals, or lie detectors adjudicate in trials, even though they do notdiscern liars from truth-tellers. I suggest that these practices owe their cultural success tocognitive mechanisms that make them culturally attractive. Informal oaths triggermechanisms of commitment in communication. Judicial oaths, by invoking supernaturalpunishments, trigger intuitions of immanent justice, linking misfortunes following an oathwith perjury. These intuitions justify the infliction of costs on oath takers in a way thatappears morally justified. Ordeals reflect the same logic. Intuitions about immanent justicelink a worse outcome following the ordeal with a guilty verdict. This link justifies theapplication of the ordeal, and the fixed costs involved (burning, poisoning). Lie detectors alsorely on the creation of a link between a specified outcome and a guilty verdict. However, theyrely on a variety of intuitions ranging from the plausibly universal to the culturallyidiosyncratic.