The classic of literary theory. According to Wikipedia: ""Johann Christoph Friedrich von Schiller (1759 – 1805) was a German poet, philosopher, historian, and dramatist. During the last few years of his life (1788–1805), Schiller struck up a productive, if complicated, friendship with already famous and influential Johann Wolfgang Goethe, with whom he greatly discussed issues concerning aesthetics, encouraging Goethe to finish works he left merely as sketches; this thereby gave way to a period now referred to as Weimar Classicism."