Some arguments seem to last forever. A perpetual argument is one that has a structure such that it goes on forever. Such an argument will terminate only when the parties are willing and able to recognize its pattern, step outside the argument, and stop it.

Suppose we label the exchanges in an argument A, B, C, ..., etc., and suppose we say that A -> B, B -> C (exchange A leads to exchange B, not implication), and so on. The perpetual argument will occur when a loop is formed, such that A->B, B->C, ..., N->A. Imagine a game of chess trapped in the draw-by-repetition-of-moves pattern. Each exchange in the argument is locally cogent, at least under the assumptions held by those promoting it, and so will continue. Such a pattern requires the intentional decision of the participants to recognize and withdraw from the exchange. Participants are not always willing or able to do this, and so a PerpetualArgument will sometimes continue for a very long time. Feedback from observers, for example marking with a CategoryPerpetualArgument badge, may invite the participants to consider whether or not they wish to continue the exchanges.

The canonical perpetual argument exists, not here on C2, but on the rec.audio newsgroup. It is the debate about which sounds better, analog or digital. It is closely related to a similar argument: which sounds better, vinyl or CD. Presumably the debate now rages about vinyl, CD and DVD. In a different domain, fisherman have a perpetual argument: Which is better, bait or lures. Psychologists love the nature versus nurture perpetual argument.

Some of the apparently perpetual arguments which have lost steam include:
* OO vs Procedural
* Relational vs everything else
* CeePlusPlus vs OO
* Whether OO "works" or not.

See HolyWar for a larger list. Please note that many of these arguments can be validly labeled as C''''''ategoryRant. YMMV.
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Discussion moved to PerpetualArgumentDiscussion