Many epistemologists endorse a view I call “evidence essentialism:” if e is evidence of h, for some agent at some time, then necessarily, e is evidence of h, for any agent at any time. I argue that such a view is only plausible if we ignore cognitive diversity among epistemic agents, i.e., the fact that different agents have different—sometimes radically different—cognitive skills, abilities, and proclivities. Instead, cognitive diversity shows that evidential relations are contingent and relative to cognizers. This is especially (...) obvious in extreme cases and in connection with epistemic defeat, but it is also very plausibly true of ordinary agents, and regarding prima facie justification. (shrink)