Reinstatement, floating conclusions, and the credulity of Mental Model reasoning

Johnson-Laird and coworkers’ Mental Model theory of propositional reasoning is shown to be somewhere in between what logicians have defined as “credulous” and “skeptical” with respect to the conclusions it draws on default reasoning problems. It is then argued that in situations where skeptical reasoning has been shown to lead to problematic conclusions due to not being skeptical enough, the bolder Mental Model theory will likewise make counterintuitive predictions. This claim is supported by the consideration of two of those situations, namely problems involving reinstatement and floating conclusions. It is discussed how the recent “principle of pragmatic modulation” could be a first step in order to overcome the mild credulity of Mental Model reasoning.