In rhetoric, a tautology (from Greek tauto, "the same" and logos, "word/idea") is a logical argument constructed in such a way, generally by repeating the same concept or assertion using different phrasing or terminology, that the proposition as stated is logically irrefutable, while obscuring the lack of evidence or valid reasoning supporting the stated conclusion. (A rhetorical tautology should not be confused with a tautology in propositional logic.)[a]
A rhetorical tautology guarantees the truth of the proposition, where the expectation (premise) was for a testable construct, any conclusion is by the precepts of falsificationism a non sequitur (logic). Circular reasoning differs from tautologies in that the premise is restated as the conclusion in an argument, instead of deriving the conclusion from the premise with arguments, while a tautology states the same thing twice. If the argument that separates the conclusion from the premise is a logical fallacy such as a rhetorical tautology, then the conclusion is merely a restatement of the premise, rather than deriving in a logical fashion from the premise. The form the arguments are allowed to take, either falsifiable or unfalsifiable, dictates in what way the conclusion can logically derive from the premise, without merely restating the premise.[clarification needed]
^Rhetorical tautologies state the same thing twice, while appearing to state two or more different things; logical tautologies state the same thing twice, and must do so by logical necessity. The inherent meanings and subsequent conclusions in rhetorical and logical tautologies or logical necessities are very different. By axiomatic necessity, logical tautologies are neither refutable nor verifiable under any condition.