Abstract
An ad hominem fallacy is committed when an individual employs an irrelevant personal attack against an opponent instead of addressing that opponent’s argument. Many discussions of such fallacies discuss judgments of relevance about such personal attacks, and consider how we might distinguish those that are relevant from those that are not. This paper will argue that the literature on bias and testimony can helpfully contribute to that analysis. This will highlight ways in which biases, particularly unconscious biases, can make ad hominem fallacies seem effective, even when the irrelevance is recognized