 The purported epistemic and metaphysical directness of introspection does not imply that we are either infallible or omniscient about our own states, since it is an open question whether all of our states are introspectible. But if introspection involves epistemically and metaphysically direct access to one’s phenomenal states, then its proper use may allow the relevant self-attributions to achieve a high degree of certainty. And some philosophers have drawn on the concept of acquaintance to argue that at least some mental states, such as intense sensations, may be “luminous”: that is, that being in a state of that kind may ensure that one can know that one is (Weatherson 2004; Duncan 2018). These arguments are responses to Williamson’s (2000) “anti-luminosity” argument, which seeks to establish that no mental states are luminous.