From Longman Dictionary of Contemporary Englishcircular argument/logic/reasoningcircular argument/logic/reasoningTHINK something/HAVE A THOUGHTan argument or way of thinking that is not right because the statement it uses to prove that the argument is true can only be true if the original argument is already true → circular
Examples from the Corpus
circular argument/logic/reasoning• Clearly the more elaborate the dress, the more dress-fasteners required, although there is here the danger of a circular argument.• Failure to recognize this leads to circular arguments.• The Court refused to allow itself to be caught in a circular argument as to which State needed to waive immunity first.• The irony in all this is the circular logic of what appears to be the new strategic competition.• Pupils can often fall back on a circular argument such as: Why is the relationship linear?• We start by talking about a problem of circular reasoning to motivate the diagram.• This appears to be a circular argument, typical of closed-belief systems. 