Your answer is accurate, but I recall a high school calculus teacher who every year began his semester with a lecture stating something absurd like this. I thankfully don’t recall the precise details, but I believe it was more to the effect of 1+1=0 or something. I know it invovled a long drawn out proof involving a variety of limit value problems, and the like. I am certain that it was a valid arguement and there was simply one minor inconsistancy which created the logical dilemma. It was of the effect that we assume some fact which is not proven in day to day math. Sorry for the vagaries, but I am not about to scrape up some old notes to clarify. I wonder if there are some teemers out there who are familiar with this and if this is the type of arguement the original question was interested in.

Link to the Mailbag Article: http://www.straightdope.com/mailbag/m2_2_5.html

Interesting thought, Omni, but I think it’s unlikely that was what the question was aimed at. The expression “2 + 2 = 5 for very large values of 2” is pretty clear, methinks.

The kind of logical inconsistency you’re thinking of usually winds up proving that 1 = 0. There is some logical flaw in the proof, often very hard to spot; a hidden division by zero is one of the most common flaws. None of those cute little exercises, so far as I know, adds a qualifier like “for very large values of 2.”

[Note: This message has been edited by CKDextHavn]