This work has been struggling with the aesthetic opposites as a fundamental and innovating a phenomenon in understanding beauty in long narrative poem "Endymion" of John Keats, in interpretative contexts of Aesthetic Realism that is a new strand in the Postmodern Aesthetic theory of Eli Siegel. The novelty of the work lies in the argument that aesthetic realism, as a strand of Aesthetic discussion, has received relatively little attention in existing interpretative engagements of English literature in Pakistan. The major issue has been a modified understanding of two Aesthetic opposites' pairs of 'Order and Freedom' and of 'Simplicity and Complexity' of Aesthetic Realism and the analysis of "Endymion" in the light of these perspectives.