We tend to conceptualize perceptual illusions as mistakes: illusions get the perceived object wrong. Developing insights from Merleau-Ponty, in the first section I challenge this view by elucidating some key experiential characteristics of illusory phenomena, to emphasize how the concept of illusions-as-mistakes relies on perspectives unavailable within illusory experiences. This perspective inclines us to introduce extrinsic, fixed norms, according to which illusions are mistakes. Described from within experience, an illusory phenomenon is not a case of mistakenly perceiving X as Y, it is rather a way that X makes a different kind of sense, in virtue of a norm that is not a fixed, objective standard, but is engendered within and endogenous to ongoing dynamics inherent in living, perceptual behavior.