The sense of conviction about the reality of a delusion is based not only on the kernel of historical truth in the content of the delusion, but also on the historical truth of ego states and functions which are regressively re-experienced during the psychosis. The basic anxiety of the psychotic patient is of dedifferentiation and ultimate loss and dissolution of the self. Dedifferentiation and blurring of ego boundaries can serve a defensive function but it is a maneuver which leaves the patient vulnerable to the most basic anxiety, i.e., destruction of the self. The formation of a delusion is restitutive in that it attempts to protect the patient against psychic disintegration. 'The delusion is necessary for the individual to survive.'