 In the conciliatory cases, self-doubting higher-order evidence acts as a defeater of justification for belief, which raises the question of its similarities to and differences from other defeaters. In John Pollock’s (1989) terminology, some defeaters of justification for a conclusion are rebutters, that is, are simply evidence against the conclusion, while other defeaters are undercutters; they undermine the relation between the evidence and the conclusion. (These are also referred to as Type I and Type II defeaters.) The pilot we imagined would be getting a rebutting defeater of her justification for believing that she had enough fuel for an extra 50 miles if she looked out her window and saw fuel leaking out of her tank. However, if the altimeter reading is a defeater, then as evidence about whether she drew the right conclusion from her evidence it is definitely of the undercutting type.