Faldage, I disagree.

In the first case, "I am." has the implied predicate "going to park with you."

In the GKC case, "I am" is short for "I exist." Of course he's saying more than that. Seems clear he was commenting on the experiences of alienation, subjugation, and depersonalization induced by the industrial revolution - the same experiences that provoked the dystopic "Metropolis."

"I AM!" or "I EXIST!" or "*I* exist!" "I am a person, dammit, an individual - not an automaton, not a group of holes punched on a Hollerith card, or a cog in the grand machine, but a human being!"

In this case, I see the implied paragraph, but I don't see the implied predicate.