The first principle is that you must not fool yourself and you are the easiest person to fool.
—Richard P. Feynman#2383•
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Affirming the consequent is a formal fallacy that takes this form: If A then C, C; hence A. The error lies in assuming that because the consequent is true, the antecedent must also be true, which in reality need not be the case.
For example, "People who go to college are successful. John is successful, hence he must have gone to college." Clearly, John's success could be a result of schooling, but it could also be a result of his upbringing, or perhaps his eagerness to overcome difficult circumstances. Generally, because schooling is not the only path to success, one cannot say that a person who is successful must have received schooling.#2388•
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Circular reasoning is one of four types of arguments known as begging the question, [Damer] where one implicitly or explicitly assumes the conclusion in one or more of the premisses. In circular reasoning, a conclusion is either blatantly used as a premiss, or more often, it is reworded to appear as though it is a different proposition when in fact it is not.
For example, "You're utterly wrong because you're not making any sense." Here, the two propositions are one and the same, since being wrong and not making any sense mean the same thing in this context.
The argument is simply stating "Because of x therefore x," which is meaningless.#2387•