Amentia, or confusion, is a state of acute hallucinatory delirium; it was described with this name by Theodor Meynert in Leçons cliniques de psychiatrie (1890). Meynert, who had been a professor of psychiatry since 1873 at the University of Vienna, believed in an anatomic-clinical theory of psychiatry and did not attribute any meaning to the hallucinations that arose during amentia, considering them merely a disorderly flow of "accessory representations" from "cortical exhaustion" and excessive irrigation of subcortical centers, which were considered to be the seat of sensory impressions.
Freud, faithful to his teacher of 1883, also referred to the clinical value of the concept of amentia, in spite of the differences between them (Jones, 1953). He wrote of "a fine daydream" (Freud, 1916-17f) and, as demonstration of this, a "hallucinatory psychosis of desire."
Although Freud mentioned the concept much earlier (1894a), it is not until his A Metapsychological Supplement to the Theory of Dreams (1916-17f) that he would see in amentia an element of comparison, with which to explain the role of belief in the hallucinatory fulfillment of desire in dreams. The regression of the preconscious to mnemic images of things invested by the unconscious would be unable to explain such belief if, in both cases, the conflict with reality (associated with the functions of consciousness) weren't eliminated. Amentia is unlike the dream state, where it is through the wish to sleep that the subject loses interest in reality. Rather, in the hallucinatory psychosis of desire, the subject denies a reality that is unbearable because of the loss it inflicts, and is thus open to the free play of hallucinatory fantasies.
See also: Delusion; Metapsychological Supplement to the Theory of Dreams, A ; Meynert, Theodor.
Freud, Sigmund. (1894a). The neuro-psychoses of defence. SE, 3: 45-61.
——. (1916-17f). A metapsychological supplement to the theory of dreams. SE, 14: 222-235.
Jones, Ernest. (1953-1957). Sigmund Freud: Life and work. London: Hogarth Press.
Meynert, Theodor. (1890). L'amentia ou confusion. In C. Levy-Friesacher (Ed.), Meynert-Freud "L'amentia." Paris: Presses Universitaires de France, 1983.