If we changed the way we count, could 2+2 fail to equal 4?  If, for example, we started counting with zero, we might count X X X as 0, 1, 2 X's.  Then 2 + 2 would equal X X X X X X, and when we counted the X's, we would count, "zero, one, two, three, four, five."  So 2+2=5.
So, does this example show that 2 + 2 doesn't necessarily equal 4?  Or, would we have to say that we were speaking another language when we truthfully say that 2+2=5?