Circular reasoning

[2] Circular reasoning is not a formal logical fallacy, but a pragmatic defect in an argument whereby the premises are just as much in need of proof or evidence as the conclusion.

As a consequence, the argument becomes a matter of faith and fails to persuade those who don't already accept it.

[3] Circular reasoning is closely related to begging the question, and in modern usage the two generally refer to the same thing.

The Pyrrhonist philosopher Sextus Empiricus described the problem of circular reasoning as "the reciprocal trope": The reciprocal trope occurs when what ought to be confirmatory of the object under investigation needs to be made convincing by the object under investigation; then, being unable to take either in order to establish the other, we suspend judgement about both.

David Hume's problem of induction demonstrates that one must appeal to the principle of the uniformity of nature if they seek to justify their implicit assumption that laws which held true in the past will also hold true in the future.