Are there any rules defining art?

In his essay, one of the issues John Cage addresses is that "art... is criminal action."  It abides by no rules he explains, but is this necessarily true?  Is there any limitation to what we consider art? It has become popular to support the theory that art is whatever the artist considers to be art, whether it is a life-like representation or merely looks like scribbles done by a five year old. While I agree with this theory that anything can be art, I don't think that means everything is art.  I believe the one rule that we can apply to art in all cases is that it must communicate something to someone, either the artist or the viewer.  In this sense, we would not really be restricting anything that we already consider art, but we would be correcting what it, in my opinion, a false statement, that art follows no rules.