Starting from atypical psychosis as a model of a psychotic entity typically associated with states of altered consciousness, and having as organic and physiological comparative models epileptic psychosis and dream, respectively, the authors seek to establish a fundamental condition for these phenomena. Then, assuming a phenomenological perspective, we analyze the latest neuroscientific findings in the field of psychosis, including schizophrenia, trying to extrapolate the findings obtained in atypical psychoses to all forms of psychosis, achieving a defining principle of psychosis. We conclude that psychosis consists in a disturbance of consciousness, namely, of a pre-reflective consciousness. This will be dependent on a complex neural system which, starting from a primordial feeling of Self, differentiates and branches out through higher brain structures along the ontogenetic development. A significant interference on the connectivity of this system leads to a commitment of effective intentionality in the psychotic individual, with a discontinuity in the search for meaning, and interaction of individuals in the world, where the regulation of primitive emotional tendencies for higher cognitive components is lost.