 In sum: states of affairs offer themselves up to systematize the relations between seeing, visual hallucination and illusion. For instance, one might suggest the following explications:  S’s experience as of a’s being F is S’s seeing a to be F, if, and only if, the state of affairs of a’s being F obtains and causes the experience in the right way; S’s experience is an illusion if, and only if, the state of affairs does not obtain; and the experience is a hallucination if, and only if, only the state of affairs of a’s being F does not exist, but its property-part does.