“Realistic, illusionist art had dissembled the medium, using art to conceal art. Modernism used art to call attention to art. The limitations that constitute the medium of the painting – the flat surface, the shape of the support, the properties of pigment – were treated by the Old Masters as negative factors that could be acknowledged only implicitly or indirectly. Modernist painting has come to regard these same limitations as positive factors that are to be acknowledged openly.” – Clement Greenberg.
Clement Greenberg, in Harrison and Wood, (eds), Art in Theory, 1960-1990, 755-6.
What a fabulous quote, it gets right to the heart of what Modernist art and painting is and explains it simply by comparing it with the art that has gone before.