Deductive reasoning Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Fallacies === Various formal fallacies have been described. They are invalid forms of deductive reasoning.<ref name="IEPFallacies">{{cite web |last1=Dowden |first1=Bradley |title=Fallacies |url=https://iep.utm.edu/fallacy/ |website=Internet Encyclopedia of Philosophy |access-date=12 March 2022}}</ref><ref name="Stump">{{cite book |last1=Stump |first1=David J. |title=New Dictionary of the History of Ideas |url=https://www.encyclopedia.com/history/dictionaries-thesauruses-pictures-and-press-releases/fallacy-logical |chapter=Fallacy, Logical}}</ref> An additional aspect of them is that they appear to be valid on some occasions or on the first impression. They may thereby seduce people into accepting and committing them.<ref>{{cite web |last1=Hansen |first1=Hans |title=Fallacies |url=https://plato.stanford.edu/entries/fallacies/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=12 March 2022 |date=2020}}</ref> One type of formal fallacy is [[affirming the consequent]], as in "if John is a bachelor, then he is male; John is male; therefore, John is a bachelor".<ref>{{cite web |title=Expert thinking and novice thinking: Deduction |url=https://www.britannica.com/topic/thought/Expert-thinking-and-novice-thinking |website=Encyclopedia Britannica |access-date=12 March 2022}}</ref> This is similar to the valid rule of inference named [[modus ponens]], but the second premise and the conclusion are switched around, which is why it is invalid. A similar formal fallacy is [[denying the antecedent]], as in "if Othello is a bachelor, then he is male; Othello is not a bachelor; therefore, Othello is not male".<ref name="BritannicaThought">{{cite web |title=Thought |url=https://www.britannica.com/topic/thought |website=Encyclopedia Britannica |access-date=14 October 2021 |language=en}}</ref><ref>{{cite journal |last1=Stone |first1=Mark A. |title=Denying the Antecedent: Its Effective Use in Argumentation |journal=Informal Logic |date=2012 |volume=32 |issue=3 |pages=327β356 |doi=10.22329/il.v32i3.3681 |url=https://philpapers.org/rec/STODTA|doi-access=free }}</ref> This is similar to the valid rule of inference called [[modus tollens]], the difference being that the second premise and the conclusion are switched around. Other formal fallacies include [[affirming a disjunct]], [[denying a conjunct]], and the [[fallacy of the undistributed middle]]. All of them have in common that the truth of their premises does not ensure the truth of their conclusion. But it may still happen by coincidence that both the premises and the conclusion of formal fallacies are true.<ref name="IEPFallacies"/><ref name="Stump"/> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page