A tautology is a statement that is true by definition. It thus shares some qualities with circular argumentation, but the principle difference lies in the fact that a tautology takes the form of a single proposition or statement whereas an argument would require an inference from one statement to another.
Note that some phrases are considered tautological in themselves, e.g. “close proximity,” but such phrases are of less interest to argument analysis than tautological statements insofar as the latter skews questions of truth value in interesting ways whereas tautological phrasing generally doesn’t.
Tautologies certainly have specific uses within formal logic and mathematical proofs. In every day speech, tautologies often draw contempt under the impression that those who produce them think they are saying something substantive, but tautologies can also provide emphasis or clarify the relationship between different terms. In some cases, context may suggest a slightly different understanding between the terms in question, thus giving tautologies a degree of substantive meaning not apparent from the surface grammar of the statement. (For example; in the Yogi Berra quote; “It ain’t over till it’s over,” the first instance of over most likely means something like “settled for practical purposes” and the second “officially completed,” leaving us with a quote about the relationship between a possible outcome and an accomplished fact. ) Tautologies can also be used to reject waffling or equivocation by another party (E.g. “Either you did or you didn’t!”).
Some of these may or may not be examples of tautological reasoning.
1: Phonological ambiguity at no extra charge!
2: Squid Reasoning (not necessarily tautological, but close enough to get a mention)
3: A circle of violence.
4: If it looks like a Tautology and quacks like a tautology…
5: The sports commentator John Madden is often credited with once saying; “They are simply going to have to score more points than the other team to win the game.” If anyone knows of an exact source, would you mind dropping me a comment?
6: “Boys will be boys.” (Common saying)
7: “There’s nothing you can do that can’t be done. There’s nothing you can sing that can’t be sung.” The Beatles, All You Need is Love, 1967.
8: “It ain’t over till it’s over,” Yogi Berra commenting on a baseball game in 1973.
9: A Whole Song!
10: This example is real, unless it isn’t.
11: Because of course it is.
13: Well, at least it was open when it was open.
14: “‘No’ means ‘no’.” (Common saying.)
15: Had this one on my bumper until I didn’t.
“Nobody’s right if everybody’s wrong” Buffalo Springfield, What What It’s Worth, 1967.