Full Idea
According to Winckelmann, the law and aim of all art is beauty, independent of goodness. The three kinds of beauty are of form, of idea, and of expression (the highest aim, attainable only when the other two are present).
Gist of Idea
Art aims only at beauty, of form, of idea, and (above all) of expression
Source
report of Johann Winckelmann (History of Ancient Art [1764]) by Leo Tolstoy - What is Art? Ch.3
Book Reference
Tolstoy,Leo: 'What is Art? and Essays on Art', ed/tr. Maude,A [OUP 1975], p.93
A Reaction
This sounds very like 'art for art's sake', but a hundred years earlier. This is quite a good distinction, and I particularly like the 'beauty of idea', which is often overlooked.