Bob, I don't think that's an aphorism.  Actually, it's an argument, and,
as a petitio principii, a faulty one.  To assert existence, I suppose,
some might say "I am."  But ordinarily that sounds empty of meaning.  I
would expect that "I am a teacher" is a more sensible use of the copula.
Crane didn't say either, "A man said to the universe, / Sir, I am."   He
said, "Sir, I exist."  I think that "John is" sounds complete only if we
are tainted by philosophical forethought, no?

==Reinhold

Bob Yates wrote:

> Just to add one more point to the "John is" construction.  One of the
> famous aphorisms in Western thought is:
>
> I think, therefore I am.
>
> I have no sense that "I am" is incomplete.
>
> Bob Yates