Proposal and Experimental Evaluation of Syllogism Examination Using Fallacy Transformations

Learning from fallacious arguments is regarded as an important component of logical thinking education; however, instructional methods that explicitly incorporate fallacies into argument examination have not been sufficiently systematized. Building on triangular logic—a graphical representation of arguments—this study proposes a fallacy-transformation–based reconstructive method for examining syllogistic arguments. In the proposed approach, learners attempt to reconstruct a logically valid syllogism by applying a transformation to one of the propositions; if validity is achieved only through a fallacious transformation (e.g., converse or inverse of an implication), the original argument is judged invalid and the transformation itself becomes the rationale for explaining the error. The method was operationalized as an online practice system and evaluated with 21 undergraduate/graduate students in information engineering who had prior experience with triangular-logic construction practice. The experiment consisted of a pre-test, instruction, system-based practice (30 items), a post-test, and a delayed test approximately two months later. Test items included cases requiring no transformation, valid contrapositive transformation, and invalid cases diagnosable via fallacious transformations. Results indicated that validity-judgment scores improved significantly from pre-test to post-test and were largely retained at delay, with large effect sizes. In addition, explanation responses shifted markedly toward method-based reasoning, suggesting that learners became able to apply the proposed examination procedure in their justification.