Specifically, my critera for art is to have none at all. It's why I love Rothko, Pollock and Jasper Johns.
It doesn't have to be a “form” or structure in some manner to stimulate me. The simplicity of Rothko's color work or Pollock's random splatter is art to me because it makes me feel and think.
Pretty simple, really.

that's an excellent way of looking at it — i may have to steal your answer now. when i think of all the things that truly inspire me, most of them are naturally occurring, or at least not specifically created to impress me.

it's odd, because i took a whole section out of this post detailing examples of innovative artists who were unbound by traditional format, and Pollock was one of them. your comment makes me think i should have kept that part in.

I think the thing with teachers (especially writing teachers) is they can only teach you what has worked in the past. Sadly that makes innovation hard to teach. I guess all you can really do is teach students how to think for themselves, and wait for the ones with the talent to pave their own way.