One place where there is a Philosophical discussion of this question is in Heidegger’s The Origin of the Work of Art (http://en.wikipedia.org/wiki/The_Origin_of_the_Work_of_Art). This is one of my favorite essays of Heidegger so I am glad to be able to mention it here.
Basically Heidegger connects Art to the interaction of World and Earth. He says that it is an endeavor what brings out the qualities of the Earth to make them visible in the World.
In this regard I like to make the distinction between Unhewn, Hewn, Rough Cut, Smooth Cut, and Formed objects.
Art supposedly allow the artist to impose his enforming on some content which are thereby turned into “Art”. But there is a kind of Japanese art called Suisek (waterstones) where one merely picks up an interestingly shaped rock and display it, and that is seen as a high form of art, where nothing is done to the object other than display it in an aesthetic context. These stones in the best cases are completely unhewn.
Here is a random example from http://britbonsaiblog.blogspot.com
I don’t know whether this example is unhewn or rough hewn. Some times they slightly polish the rocks. But you can see how this found rock has been presented in an aesthetic setting.
So what Heidegger is saying is that when ever we create a clearing and then bring something into it for presentation by uncovering the earthy qualities of the thing then we are producing art, and unhewn and unpolished Suiseki is an extreme example of that. So art from Heidegger’s viewpoint is not the fact that the artist is imposing his will on the materials and thus bringing the form into being, but his point is that it is when the content is exposed by the forming process such that we see its texture, pattern, and motility then that is art. Heidegger is striving for a non-subjective and non-objective definition of art, in which the underlying substance that the artist is working with is heard speaking to us in a unique manner. Art is then a process of disclosing the vision of the earth, within the clearing of the world that we provide. Everything else that makes up art as we know it is piled upon that fundamental phenomena of disclosure of earth’s qualities within light provided by our worldmaking.