The paper argues that the two best known formal logical fallacies, namely denying the antecedent (DA) and affirming the consequent (AC) are not just basic and simple errors, which prove human irrationality, but rather informational shortcuts, which may provide a quick and dirty way of extracting useful information from the environment. DA and AC are shown to be degraded versions of Bayes’ theorem, once this is stripped of some of its probabilities. The less the probabilities count, the closer these fallacies become to a reasoning that is not only informationally useful but also logically valid.
KeywordsAffirming the consequent Bayes’ theorem Denying the antecedent Formal fallacies Rationality
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- Aristotle, (1938). De Sophisticis Elenchis. On sophistical refutations (trans: Forster, E. S.). On with the Cosmos/by Furley, D. J. Cambridge, MA: Harvard University Press.Google Scholar
- Chater N., Oaksford M. (2008) The probabilistic mind: Prospects for Bayesian cognitive science. Oxford University Press, OxfordGoogle Scholar
- Griggs R.A., Cox J.R. (1982) The elusive thematic-materials effect in Wason’s selection task. British Journal of Psychology 73: 407–420Google Scholar
- Hamblin C.L. (1970) Fallacies. Methuen, LondonGoogle Scholar
- Hansen, H.V., Pinto, R.C. (eds) (1995) Fallacies: Classical and contemporary readings. University Park, PA, Pennsylvania State University PressGoogle Scholar
- Josephson J.R. (2000) Smart inductive generalizations are abductions. In: Flach P.A., Kakas A.C. (eds) Abduction and induction: Essays on their relation and integration. Kluwer, Dordrecht, BostonGoogle Scholar
- Stein E. (1996) Without good reason: The rationality debate in philosophy and cognitive science. Clarendon Press, OxfordGoogle Scholar
- Verschueren N., Schroyens W., Schaeken W., d’Ydewalle G. (2001) Why do participants draw non-valid inferences in conditional reasoning? Current Psychology Letters: Behaviour, Brain, & Cognition 6:57–70Google Scholar
- Wason P.C. (1966) Reasoning. In: Foss B.M. (eds) New horizons in psychology. Penguin, Harmondsworth, pp 135–151Google Scholar
- Woods J., Walton D.N. (1982) Argument : The logic of the fallacies. McGraw-Hill Ryerson, TorontoGoogle Scholar