John Milton's Paradise Lost - Bloom's Modern Critical Interpretations

God and Christ in Paradise Lost embody reason and restraint—but a poet is by necessity of the party of energy and desire; reason and restraint cannot furnish the stuff of creativity.

So Milton, as a true poet, wrote at liberty when he portrayed Devils and Hell, and in fetters when he described Angels and God. For Hell is the active life springing from energy, and Heaven only the passive existence that obeys reason.