Abstract. This article sketches out a metapsychology of psychosis, by focusing on the description only of the psychic processes that are specific to each psychotic disorder, so as to reveal what kind of logic is specific to it, and to hignlight the space or time dimension that is passed over by the patient. Indeed, speeches and behaviours in psychosis often seem inconsistent to us, but they follow logical psychic processes that are specific to each disorder, as this article intends to show from patient cases. It deals with how missed experiences of space and time lead psychotic patient to follow imaginary logics, also called formal logics by logicians as they ignore one of the space and time dimensions in their experience, whereas nevrotic patients would follow empirical logics in similar situations. Thus, each psychotic disorder follow a specific imaginary logic : the psychic process specific to autism follows a trivalent or fuzzy logic, that of schizophrenia follows a epistemic or non-monotonous logic, that of paranoia follows a repetitive or fractal logic, and that of bipolar disorder follows an associative logic, which psychosis clinicians respectively call indeterminacy, delusion, ritualization and disjointed speech.