I don’t know if anyone will read this at this late date, but what lesson one would naturally learn from this situation largely depends on one’s temperament. And usually, a person of a particular temperament would assume that his lesson was the only lesson worth learning. The answers above illustrate this point in spades.
Few Sunday strips by Bill Watterson show his brillance better than this one, leaving it open-ended as he did.
The lesson I got? Being an ENFP like Calvin, I tend to come up with the same uncomfortable ambiguity he does. :)