 In the context of the Problem of Perception, these cases are usually distinguished as follows: a veridical experience is an experience in which an ordinary object is perceived, and where the object appears as it is; an illusory experience is an experience in which an ordinary object is perceived, and where the object appears other than it is; a hallucination is an experience which seems to the subject exactly like a veridical perception of an ordinary object but where there is no such perceived or presented object. (For illusions and hallucinations which don’t fit these forms, see Johnston (2011), and Batty and Macpherson (2016)).