Later in life Frye said that if he had it to do over he would not write a sophisticated academic work about Blake, but something more like Percival's introductory survey. He called his last (monumental!) two volume work The Great Code of Art or The Bible as Literature. That's an invaluable work for learning Blake.
In Britain's early 19th Century the Enlightenment had a marked effect on religious thought; Deism was ascendant, the idea that God created the world and wound it up like a clock and thereafter retired from any interest in it. We are to God what ants are to us.
As you can imagine Bible soaked and God intoxicated Blake despised Deism. But he equally despised what he took to be the opposite, which he called (among other things) Druidism, the most primitive form of religion, including human sacrifice.
Druidism fit Blake's concept of established religion, whose leaders enthusiastically supported the king's wars; in the same way the religious leaders today have emphatically supported the government's wars. (The government, established religion and the military industrial complex were like three peas in a pod in Blake's day.)
Here's one of Blake's reactions to that sad reality:
(Plate 11) (of the Marriage of Heaven and Hell)
"The ancient Poets animated all sensible objects with Gods or Geniuses, calling them by the names and adorning them with the properties of woods, rivers, mountains, lakes, cities, nations, and whatever their enlarged & numerous senses could percieve.
And particularly they studied the genius of each city & country, placing it under its mental deity.
Till a system was formed, which some took advantage of & enslav'd the vulgar by attempting to realize or abstract the mental deities from their objects; thus began Priesthood.
Choosing forms of worship from poetic tales.According to Blake God is within-- you and me, everyone. In this he closely resembled the Quakers who fundamentally speak of that of God in you/me/everyone. The God within is creative, a Creator of Art. This depends upon imagination, intuition, the expression of spiritual/eternal ideas in tangible things-- like words (the Bible), music, and representations of the human form in its various states.
And at length they pronounc'd that the Gods had order'd such things.
Thus men forgot that All deities reside in the human breast."
Here's an example in the Laocoon (E274) of how Blake expressed this idea:
"Prayer is the Study of Art
Praise is the Practise of Art
Fasting &c. all relate to Art
The outward Ceremony is Antichrist
Without Unceasing Practise nothing can be done
Practise is Art If you leave off you are Lost
A Poet a Painter a Musician an Architect: the Man
Or Woman who is not one of these is not a