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The Rationality of Informal Argumentation: A Bayesian Approach to the Fallacies

Ulrike Hahn  
School of Psychology , Cardiff University, UK  

Classical informal reasoning "fallacies," e.g., begging the question or arguing from ignorance, while ubiquitous in everyday argumentation, have been subject to little systematic investigation in cognitive psychology . In Oaksford and Hahn (2004) and Hahn and Oaksford (in press) we recently presented a Bayesian analysis of several key fallacies. The talk will outline our Bayesian account of argument strength and its application to the fallacies 'argumentam ad ignorantiam, the circular argument or petitio principii, and the slippery slope argument. It will also presents experimental data demonstrating that people are sensitive to the key factors affecting argument strength according to the Bayesian account.