Abstract Expressionism

I must admit I could not and still do not understand Clement Greenburg's 'Modernist Painting', although not through lack of trying. His writing is far above the level of a student freshly out of yr 12 bottom English, such as myself, but i will try to reveal the small amount took from it.
The Abstract expressionist movement came at a time when the American economy was flourishing due to the end of WWII and secured New York City as center of Western art. According to Greenburg, artists of this time were steering away from the three dimensional form as to try and achieve "purity" through two-dimensionality as that is a characteristic that painting shares with no other art form. Greenburg says "One is made aware of the flatness of their pictures before, instead of after, being made aware of what the flatness contains. Whereas one tends to see what is in an Old Master before seeing it as a picture...". To me this is the definition of modernist abstract expressionism, or at least the difference between the latter and previous movements.
Through Jackson Pollock, Robert Hughes' "An Empire of Signs" regards abstract expressionism as an art form which lets the artist paint within their primal instincts in a very primitive way. Pollock says he wishes to "be nature, not just paint it" and though some may see nothing more than random brush strokes, to many it is undeniable that the sense of nature comes through in his work. Clement Greenburg even described him as the "best living American artist". Jackson Pollock was very influential to aspiring expressionists as he unlocked a whole new world with his fresh ideas of surface and touch.