"When is art?" a good or bad way to critique a work of art?

In my opinion Goodman’s “when is art” instead of “what is art" is a good way to view pieces of art due to the fact that he provides a set of standards in which one can see when an object becomes a piece of art. I completely agree that a work of art is seen as such when it is displayed in a certain way, for example one would not see a painting as a work of art if it were being used as a floor mat, it would most likely be seen as a work of art when it is displayed in a more formal setting such as a museum. Also I think in some sense it is true that objects are made into works of art due to the fact that we treat them in a certain way. For example if the 
Mona Lisa was not displayed in a very popular,museum surrounded by a countless number of security guards, it probably would not be seen as such a valuable art piece. I think the question when does an object become a work of art is a more easily answered question the defining what art truly is. Defining are sets a concrete definition and set of standards that a work must follow in order to be considered a work of art, unlike when one looks as when something is seen as a work of art. (it allows more room for interpretation)