Intended Art

In class yesterday we discussed the importance of "Intended Art".
In the conversation the blank canvas example from the introduction to "Nature of Art" and John Cage's 4:33 (a silent piece of music) were both brought up. Many people experiencing the pieces for the first time would not defend either of the pieces as works of art because anyone could create those pieces with minimal effort. However, because an artist put the thought into creating such a piece and intended it to be art, it is art. Perhaps a blank canvas is not visual art, or a silent song is not music, but rather both pieces can be considered a form of performance art.
To me the canvas would represent the beginnings of the creative process for an artist. A piece of pure, blank and inspiring white canvas.
4:33 is quite theatrical. The conductor moves slightly, but the entire orchestra remains motionless. The entire piece continues on this way until the end of four minutes and thirty three seconds.
No matter how simple or complex the art is, it will always be art because of the intentions of the artist who created the pieces.
Can something found in nature be considered art if picked up by a human and called art?