An informal fallacy is an argument whose stated premises fail to support their proposed conclusion.1 The deviation in an informal fallacy often stems from a flaw in the path of reasoning that links the premises to the conclusion. In contrast to a formal fallacy, the error has to do with issues of ratiocination manifest in language used to state the propositions; the range of elements that can be symbolized by language is broader than that which the symbolism of formal logic can represent. Informal fallacies of deductive reasoning contain a fundamental disconnect between the premises and the conclusion that renders the argument invalid. This disconnect often stems from the presence of a hidden co-premise that, if presented, would validate the argument.
Inductive informal fallacies are slightly different than their deductive counterparts, as their merit rests in the inductive strength of the premise-conclusion link rather than in the presence of hidden premises. For instance, the fallacy of hasty generalisation, can be roughly stated as:
- p) S is a P
- p) S is also a Q
- c) therefore, all Ps are also Qs
If the populations of P and Q are both too large to sample completely, then the statement is inductive. In such a case, a hasty generalization occurs when the number of Ps and Qs is insufficient to represent the respective populations.2 It is important to distinguish between a principle of reasoning (deductive or inductive) and the premise of an argument.
See also
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References
- ^ Kelley, D. (1994) The Art of Reasoning. W W Norton & Company, Inc. ISBN 0-393-96466-3
- ^ In other words, when you fail to mind your Ps and Qs!
Further reading
- Damer, T. E.; Rudinow, J.; Barry, V. E.; Munson, R.; Black, A.; Salmon, M. H.; Cederblom, J.; Paulsen, D.; Epstein, R. L.; Kernberger, C.; Others, (2009). Attacking Faulty Reasoning: A Practical Guide to Fallacy-Free Arguments (6E ed.), Wadsworth. ISBN 9780495095064, http://www.duxbury.com/cengage/instructor.do?product_isbn=9780495095064&disciplinenumber=5.
External links
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