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What is circular reasoning?
Circular reasoning (also known as paradoxical thinking[citation needed] or circular logic), is a logical fallacy in which "the reasoner begins with what he or she is trying to end up with." The individual components of a circular argument will sometimes be logically valid because if the premises are true, the conclusion must be true, and will not lack relevance. Circular logic cannot prove a conclusion because, if the conclusion is doubted, the premise which leads to it will also be doubted. Begging the question is a form of circular reasoning.
Circular reasoning is often of the form: "a is true because b is true; b is true because a is true." Circularity can be difficult to detect if it involves a longer chain of propositions. Academic Douglas Walton used the following example of a fallacious circular argument:
Wellington is in New Zealand.
Therefore, Wellington is in New Zealand.
He notes that, although the argument is deductively valid, it cannot prove that Wellington is in New Zealand because it contains no evidence that is distinct from the conclusion. The context – that of an argument – means that the proposition does not meet the requirement of proving the statement, thus it is a fallacy.