I need at least 8 posts to do justice to The Fall as Blake understood it. The Fall (as a preliminary to the Redemption and Return is a fundamental facet of his myth. Throughout his Complete Works he presented it in a thousand ways. It has been discussed repeatedly in this blog (look first at Urizen's Confession, which actually deals with the Fall and the Rise).
The Four Zoas might well be considered an initial sketch for Blake's myth, and it has much to tell us about The Fall:
Albion went to Beulah for R and R; he divided into the Four Zoas. Albion fell asleep after delegating the leadership to Urizen;
In Night V we hear Urizen's confession:
"O Fool could I forget the light that filled my bright spheres
Was a reflection of his face who calld me from the deep?
I well remember for I heard the mild & holy voice saying
'O light spring up and shine' and I sprang up from the deep
He gave to me a silver scepter & crownd me with a golden crown and said
Go forth & guide my Son who wanders on the ocean."
The golden crown and the silver scepter (signifying love) signified the leadership; it included the material sun signifying Light; Urizen was the charioteer of the sun pulled by the horses of Light (instruction and a few other things).
On a fateful night of drunkeness Urizen gave Luvah his "steeds of Light":
"I went not forth. I hid myself in black clouds of my wrath
I calld the stars around my feet in the night of councils dark
The stars threw down their spears and fled naked away.
Four Zoas, Night 5, 64:20-28, (E 344)
We fell! What a pregnant statement! The course of the Fall was thuswise; according to Damon (p. 419):
"the cause of Urizen's downfall into the state of Satan was that of the traditional (Miltonic?) Satan: the desire for dominion" (to attempt to dominate others is a way to fall into a state of Satan).
Urizen's loss of his "immortal steeds of light" to Luvah is a central metaphor mentioned often in 4Z. Some of its incidents may be explored in another post, but here is one of Urizen's emanation, Ahania's laments that revealed to some extent what happened:
"Ahania bow'd her head & wept seven days before the King [Urizen of course]
And on the eighth day when his clouds unfolded from his throne
She rais'd her bright head sweet perfumd & thus with heavenly voice
O Prince the Eternal One hath set thee leader of his hosts
Leave all futurity to him Resume thy fields of Light
Why didst thou listen to the voice of Luvah that dread morn
To give the immortal steeds of light to his deceitful hands
No longer now obedient to thy will thou art compell'd
To forge the curbs of iron & brass to build the iron mangers
To feed them with intoxication from the wine presses of Luvah
Till the Divine Vision & Fruition is quite obliterated
They call thy lions to the fields of blood, they rowze thy tygers
Out of the halls of justice, till these dens thy wisdom framd
Golden & beautiful but O how unlike those sweet fields of bliss
Where liberty was justice & eternal science was mercy
Then O my dear lord listen to Ahania, listen to the vision
The vision of Ahania in the slumbers of Urizen
When Urizen slept in the porch & the Ancient Man was smitten"