Logic and/in psychology: The paradoxes of material implication and psychologism in the cognitive science of human reasoning

Abstract

This chapter addresses recent critiques of the mental models theory because of its apparent endorsement of the paradoxes of material implication as valid inferences. It suggests that these critiques are guilty of psychologism, the claim that logic is descriptive of the laws of thought. This fallacious interpretation of logical systems is rife in the psychology of reasoning and leads to a confounding of logical validity and psychological validity. Just because an inference, e.g., p to if p then q (one of the paradoxes), is logically valid does not mean it is psychologically valid. There are many logics in which it is not logically valid either. The chapter traces the textual evidence for various authors making an apparent commitment to psychologism. It concludes by arguing that there is a functional mismatch between classical logic at the computational level and the mental models algorithmic level theory.