An indispensable factor or aspect of every true psychosis is mental deterioration. It has been unduly neglected by theoretical psychiatry in diagnosis, although it has been given at least a modicum of its real psychiatric value by the legal profession, by jurists, and by rating boards. The use of intellectual deterioration as the deciding criterion would make the diagnosis more certain because it can be determined by an "instrument of relative precision." No psychosis exists without its intellectual sag. Some of the ways in which this is shown are lessening of the power of memory and of recall, derangement of conceptual association (giving rise to a tendency to avoid concrete thought), lessening of personal purposiveness, impairment of judgment, and terminal dementia to almost the vegetative status. (PsycINFO Database Record (c) 2006 APA, all rights reserved)