ABSTRACT
Different syllogistic forms are analyzed with respect to the set relationships that must hold between the terms in their premises in order for them to be valid syntactically and semantically at once. It is argued that much of our seeming illogic can be attributed to conflict between relationships semantically entailed by the terms of the argument and those described through its syntactic structure. To test this hypothesis, people were asked to judge the validity of syllogisms whose semantic implications were consistent, conflicting, or moot with respect to their syntactic implications. The results indicate, in keeping with our hypothesis, that people's inferences are strongly influenced by the semantic constraints of an argument. The discussion focuses on problems involved in communicating logical relations through natural langauge.
