ABSTRACT
INABILITY to reason logically about the relationships between objects and events is a major aspect of schizophrenia, and unconventional modes of drawing inferences about the meaning of one's experience usually identify a significant disturbance of thought processes. Arieti (1955, pp. 189-273) devotes considerable attention to the schizophrenic's tendency to "retreat from reason," and a review of his excellent discussion will provide a good introduction to psychodiagnostic indi-
. cators of pathologic reasoning. Arieti bases his analysis of disturbed reasoning on the concept of
predicate thinking formulated by Von Domarus (1944). According to this concept, the schizophrenic reasons illogically because he accepts identity on the basis of identical predicates, whereas according to conventional, Aristotelian logic, identity is justified only by identical subjects. In conventional logic, for example, if all dogs have four legs and Fido is a dog, then Fido may beassum~d to have four legs; Fido and four legs can be identified because they are aspects of the same subject, dogs. Following predicate logic, howe~er, if dogs have four legs and horses have four legs, then horses are dogs because they share the same predicate, four legs. Arieti (1955, p. 195) quotes the predicate thinking of a woman who thought she was the Virgin Mary: "The Virgin Mary was a virgin; I am a virgin; therefore, I am the Virgin Mary."
