I have an anecdotal bit to add to this. I used to have a little black cat
named Shadow. I would set up my easel in the living room and paint. Once,
when I left the room, I came back to find a strange black streak on my
painting. I painted over it and thought nothing more of it...until, it
happened again. Now, understand, this painting is up on an easel, not on the
floor. I finally caught Shadow in the act. She actually dabbled her paw in
the paint on the table and stretched over to the canvas to make her mark.
Now, it was a definately deliberate act, but was it art?