  The disjunctivist may try to explain the fact that illusions and hallucinations can have the same kinds of behavioural effects as veridical perceptions by simply appealing to the fact that such experiences can be subjectively indistinguishible from veridical perceptions. Since the difference between a hallucination and a veridical perception may be something that a subject is unable to detect through introspection, the hallucination will naturally give rise to effects that are similar to those of the veridical perception. The subject will respond to such a hallucination in the same kind of way in which she would respond to a veridical perception. And there is a sense in which this response can be regarded as rational.