I found this article very interesting below are some highlights:
…something that reveals the essential or hidden truth
9. To me the thing that art does for life is to clean it – to strip it to form.
– Robert Frost (1874–1963), American poet, in Fire and Ice: The Art and Thoughts of Robert Frost, by Lawrence Thompson (1942)
…thought expressed through form (or not)
14. Ideas alone can be works of art….All ideas need not be made physical.…A work of art may be understood as a conductor from the artist’s mind to the viewer’s. But it may never reach the viewer, or it may never leave the artist’s mind.
– Sol LeWitt (1928–2007), American artist, "Sentences on Conceptual Art," in Art and Its Significance, edited by Stephen David Ross (1994)
…communication of feelings
22. Art has to move you and design does not, unless it's a good design for a bus.
– David Hockney (1937–) British artist, to The Guardian on October 26, 1988
…whatever is displayed in a museum or gallery
26. [In 1917, Marcel Duchamp, using the pseudonym R. Mutt, submitted a store-bought urinal, which he titled “Fountain,” to an art exhibition.] Whether Mr. Mutt with his own hands made the fountain or not has no importance. He chose it. He took an ordinary article of life, placed it so that its useful significance disappeared under a new title and point of view (and) created a new thought for the object.
– Marcel Duchamp, Beatrice Wood, and Henri-Pierre Roché, The Blind Man, 2ndissue (May 1917)
27. If one general statement can be made about the art of our times, it is that one by one the old criteria of what a work of art ought to be have been discarded in favor of a dynamic approach in which everything is possible
– Peter Selz (1919- ) German-born American art historian, Art in Our Times (1981)