The project of investigating the subject’s inner space as put forth in twentieth century French literature and philosophy takes on a shape which resembles an extreme form of mysticism. For Maurice Blanchot, Georges Bataille and Henri Michaux, this enquiry leads to an encounter with an existential situation which, radically different from all usual experience, presents a challenge to philosophical reflection. Therefore, to describe the mental state of exception at stake here, these writers resort to the registers of poetic language, of painting and of cinematography. Thus, by exploring an exceptional state of mind, be it a drug-induced or spiritual ecstasy, they seek to sound the depth of the involuntary operations and the hallucinatory images of the subject’s inner space.