The word “psychosis,” designating a group of serious psychical pathologies, has, since 1850, gradually replaced the word “madness” in the psychiatric literature. Without any consensus on a precise etiology of all kinds of psychosis, there is a large convergence on a clinical diagnostic with one main symptom: the loss of a sense of reality. This loss is supposed to derive from an alteration of the body diagram of the subject. This alteration implies the nonseparation between the subject and the word, and then, a blockage of any authentic communication with the Other. Being so blocked, the temporal perception impeaches the fulfilling of the subjectivity’s usual goals. The loss of reality could also induce delirium, which tries to rebuild another kind of relation with the world. It is ultimately to this last issue that psychosis brings us, inciting us to become aware of the settling in of psychotic distortion, which is already present in ordinary perspective life, because our life is frequently inhabited by dreams, ghosts, and also hallucinations. Therefore, we need to examine and question the meaning and the legitimacy of the strict border currently established between reason and insanity.