Deductivism is explained and defended. The thesis holds that logic generally, both formal and informal, is primarily concerned with the normative distinction between good and bad reasoning, and interprets good reasoning as minimally deductively valid inference. If deductivism is true, then it follows that all fallacies of reasoning, including the so-called informal or rhetorical fallacies, are deductively invalid. Deductivism as an ideology nevertheless cuts across the distinction between formal and informal logic. To defend deductivism against potential counterexamples, it is necessary to show that common fallacies are reconstructible as deductively invalid inferences. The present essay undertakes the groundwork of such a defense by arguing that even inductive argumentation, including inductive fallacies, along with circular reasoning, can be interpreted deductively. A large selection of other informal fallacies are also reconstructed as explicit deductive invalidities following a pattern that can be used to bring other fallacies under the deductivist umbrella.
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