Defeater

A defeater of a belief is evidence that this belief is false. Defeaters are of particular interest to epistemology because they affect whether a belief is justified. An important distinction is between undercutting and rebutting defeaters. Undercutting defeaters remove evidential support for a belief while rebutting defeaters provide evidential support for the opposite thesis of the belief. Defeaters play a central role in modern developments of defeasible reasoning.