Circular Reasoning

Circular reasoning smuggles the conclusion into the premises, so the argument goes in a loop and proves nothing new. "This law is just because it's the law, and we must follow the law because it's just." Each half leans on the other; nothing outside the circle is ever established.^[1] A close cousin, begging the question, does the same in one step ("Reading is important because it matters to be literate"). It can slip past because a valid argument's conclusion really does follow from its premises — the trick is that here the premise was the conclusion all along.