 All undercutters are evidence that has implications about the relation between evidence and conclusion, and to that extent are higher-order evidence. But the higher-order evidence that leads to self-doubt is distinct from other undercutting-type evidence. In the classic Type II defeater case one’s justification for believing a cloth is red is that it looks red and then one then learns that the cloth is illuminated with red light. This evidence undermines your justification for believing that the cloth’s looking red is sufficient evidence that it is red, by giving information about a feature of the lighting that gives an alternative explanation of the cloth’s looking red. This is higher-order evidence because it is evidence about the cause of your evidence, and thereby evidence about the support relation between it and the conclusion, but higher-order evidence in the cases of the doctor and the pilot are not about how the evidence was caused, and not directly about how matters in the world relevant to one’s conclusion are related to each other. 