 The debate is over whether Marr’s theory allows two subjects, call them V and V*, to have different visual contents, when V is a normal perceiver on earth, and V* is an intrinsic duplicate of V, with the same gray arrays as those had by V, and undergoes the same sequence of computations, viewed internally. V*’s gray arrays, however, have different distal causes. Borrowing an example from Burge (1986), suppose that V’s gray arrays are typically caused by shadows, and occasionally caused by cracks; whereas V* lives in a world where the optical laws are different, and there are no instances of the sort of shadows that cause V’s gray arrays. According to Burge, Marr’s theory says that the contentful visual states that are computed from V’s gray arrays always represent shadows, and thus the ones that arise from gray arrays caused by cracks are misperceptions; while the contentful visual states that are computed from V*’s gray arrays represent cracks. Neither V nor V* can discriminate the relevant sorts of cracks from the relevant sort of shadows, but according to Burge this is not sufficient to make their contents the same. According to Gabriel Segal, in contrast, the contentful visual states computed from both V and V*’s gray arrays represent a property more general than the property of being a crack or the property of being a shadow—a ‘crackdow’. (For further discussion, see Matthews 1988, Burge 1988, Davies 1991, Shapiro 1993, Egan 1991, and Patterson 1996.)