Affirmative Conclusion From A Negative Premise
Affirmative conclusion from a negative premise (illicit negative) is a formal fallacy that is committed when a categorical syllogism has a positive conclusion and one or two negative premises. For example: :''No fish are dogs, and no dogs can fly, therefore all fish can fly.'' The only thing that can be properly inferred from these premises is that some things that are not fish cannot fly, provided that dogs exist. Or: :''We don't read that trash. People who read that trash don't appreciate real literature. Therefore, we appreciate real literature.'' This could be illustrated mathematically as :If A \cap B = \emptyset and B \cap C = \emptyset then A\subset C. It is a fallacy because any valid forms of categorical syllogism that assert a negative premise must have a negative conclusion. See also * Negative conclusion from affirmative premises, in which a syllogism is invalid because the conclusion is negative yet the premises are affirmative * Fallacy of exclusive premises A ...
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Formal Fallacy
In philosophy, a formal fallacy, deductive fallacy, logical fallacy or non sequitur (; Latin for " tdoes not follow") is a pattern of reasoning rendered invalid by a flaw in its logical structure that can neatly be expressed in a standard logic system, for example propositional logic.Harry J. Gensler, ''The A to Z of Logic'' (2010) p. 74. Rowman & Littlefield, It is defined as a deductive argument that is invalid. The argument itself could have true premises, but still have a false conclusion. Thus, a formal fallacy is a fallacy where deduction goes wrong, and is no longer a logical process. This may not affect the truth of the conclusion, since validity and truth are separate in formal logic. While a logical argument is a non sequitur if, and only if, it is invalid, the term "non sequitur" typically refers to those types of invalid arguments which do not constitute formal fallacies covered by particular terms (e.g., affirming the consequent). In other words, in practice, "''non s ...
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