God and the Devilor
"Without contraries is no progression" (MHH; plate 3; Erdman 34)
That comes early in Blake's corpus and remained until the end. The end of course is Union (Oneness), when all is at rest.
Hot and Cold
Large and Small
Innocence and Experiece
Heaven and Hell
Fall and Redemption
and many, many others.
Blake adds Sun and Moon.
Joy and Woe
Pleasure and Pain
Hard and Easy
We live in a world where thought and communication are dualistic; it's very hard to get away from that although some philosophers attempt to overcome it--with success or failure.
Once again the primary contrary is contained in the (triple) title. Check the labels on the sidebar, and you may find 34 posts with God and none with Spectre (but 18 with Annihilate!)
Blake began his life with negative feelings about God (remember the angry God in the window?), especially the O.T. God. As he matured, it moderated, but (like most ordinary Bible readers today) he preferred the N.T. God over the O.T. one.
Blake's idea of God developed over his lifetime, as did his Devil (whom he most often referred to as his Spectre). That is true not just of Blake, but of anyone with a spiritual life: The God you may have worshipped at age 10 is likely not the same God you may worship today. Likewise with the Devil!
Our Father which is in Heaven; hallowed be thy name.
To worship God is this way intails recognizing Him as the primary force of your life, and obeying his directions.
Otherwise your Spectre assures you that you are in charge:
"I am the master of my fate, I am the captain of my soul." (Invictus).
You don't look to the Father; you look to yourself (your Spectre).
These two contraries are in continuos tension (conflict) until that day when it is resolved and you become a man; you are Man.
(For advanced students: with the Blake Concordance follow the two words (God and the Spectre or Jesus and the Spectre), and you may get a better grasp of Blake's spiritual development and religion.)