Full understanding of Blake's vision of God depends upon a grasp of his concepts of time and eternity. For Blake the eternal is the realm of the real, while time is the dimension of Plato's mortal cave of phantasmal dreams. Although the eternal is immortal, it does not refer simply to the hereafter; that would be just a phantasmal portion of time stretched out indefinitely. The eternal is the Mental, the Imaginative, the world to which a man may awaken as soon as he realizes that the corporeal, temporal, materialistic framework of reality is an illusion.
The rationalists of Blake's day with their radical materialism had closed themselves off from the eternal. They had imprisoned themselves in what he called the mundane shell (Milton plate 17 line 16ff). They were exclusively this worldly. Blake perceived that they worshipped the God of this World, no matter what they called him. They had most often called him Jehovah or Jesus. As a young man Blake renamed him Urizen . He spent half a lifetime studying this God of the timebound so he could cast him off and replace him with a more authentic image. Eventually he came to realize that this god's truest name is Satan. He also referred to him as the Selfhood (Jerusalem 5:21-23) and the Spectre.
Jerusalem, Plate 6
Blake tells us that radical materialism with its worship of the God of this World is a state of mind from which a man may awaken at any moment into a realization of the infinite and of his kinship with the Divine Man, Jesus. So these two Gods, the Satan of the World and the Jesus of Eternity, remain in continuous opposition in men's minds, and they are best understood in contrast to one another.
Jesus is the Lord of the Eternal realm, which is imaginative, creative, non-violent, gracious, and above all forgiving and uniting into life. Satan is God of this World, of power, might, law, man against man, separation, finally death. One is Lord of Life, the other the Lord of Death. Satan is actually not a person but a state and will eventually go to his own place, which is a way of saying that Jesus will eventually get him off our backs. This happens at the Last Judgment when all Error is burnt up.