Lecture 19

Abstract

Learning about hallucinations, which we merely touched on in previous discussions, is probably the most important topic in the general pathology of mental illness; and we therefore have to know about their basic features before we can proceed to studying examples of the various clinical pictures seen in acute psychoses. Since the time of Esquirol [1], sensory perceptions have been differentiated into two major groups: hallucinations and illusions. Hallucinations are sensory perceptions that occur without excitation of the relevant sense by any external object or external stimulus; illusions are false perceptions—misconceptions in perception of objects that are actually present. For the purposes of our schema, hallucinations belong to the group of psychosensory hyperaesthesias (p. 13); that is, they represent a pseudo-identification produced by aberrant stimuli; illusions are attributable to psychosensory paraesthesias; that is, they represent a falsification at the level of secondary identification.