[The hallucination: a perception deficit]

To be able to understand the reality of perception as much as the reality of hallucinations, it is necessary to start from notions that, placing in doubt those of "common sense", make possible: a) recognize the psychic structure essentially different from the imaginary phenomena of hallucination (Henri Ey talks about "heteronomy"), and b) understand that heteronomy express the desorganization of the perceptive act. Thereby, it is showed that the hallucination is a "false perception" and not a way of "further perception", as it is deduced from the series of DSM. Because of that Ey says that hallucination is essentially "factic" in the double sense of the term, of being a clinical fact as well as being characterized as an irruption of irreality.