Suppose you see that a red light is shining at the wall before you, or that the painter tells you that the wall is white. When this happens, your perceptual justification for believing that the wall is red is typically defeated. In the last few years there has been a surge of attention to the topic of defeaters. Symptoms and consequences of this are, for example, Sudduth (2017)’s entry “Defeaters in Epistemology” of the Internet Encyclopedia of Philosophy, and Grundmann (2011)’s chapter “Defeasibility Theories” of the Routledge Companion to Epistemology (edited by Bernecker and Pritchard). The expression “epistemic defeasibility” refers to a belief’s or a proposition’s liability to lose, have it downgraded or be prevented from acquiring some positive epistemic status, such as—for instance—being justified, being warranted or being knowledge. An epistemic defeater—possibly coinciding with an experience, a reason, a belief or a fact—is, broadly speaking, what actualizes this possibility.