In the Biblical story of the Prodigal Son the younger son arrives at the point of despair after having separated himself from his family and exhausted his resources:
 And not many days after the younger son gathered all together, and took his journey into a far country, and there wasted his substance with riotous living.
 And when he had spent all, there arose a mighty famine in that land; and he began to be in want.
 And he went and joined himself to a citizen of that country; and he sent him into his fields to feed swine.
 And he would fain have filled his belly with the husks that the swine did eat: and no man gave unto him.
 And when he came to himself, he said, How many hired servants of my father's have bread enough and to spare, and I perish with hunger!
Job reached a similar point of hopelessness and darkness which Blake picture in Plate 8 of his Illustrations to the Book of Job.
Illustrations to the Book of Job
Plate 8, Linnell Set
 After this opened Job his mouth, and cursed his day.
 And Job spake, and said,
 Let the day perish wherein I was born, and the night in which it was said, There is a man child conceived.
 Let that day be darkness; let not God regard it from above, neither let the light shine upon it.
 Let darkness and the shadow of death stain it; let a cloud dwell upon it; let the blackness of the day terrify it.
 As for that night, let darkness seize upon it; let it not be joined unto the days of the year, let it not come into the number of the months.
 Lo, let that night be solitary, let no joyful voice come therein.
The term that Blake used for the real or authentic humanity which resides within each individual is the Identity. This is the part of us that is connected to the Eternal and is Eternal itself. When an individual ascribes to false ideas or acts in inauthentic ways the Identity may be obscured or may enter a state like sleep. The Selfhood occupies the position vacated by the Identity and the connection with the Eternal is broken. If the individual could 'come to himself' as did the Prodigal son, the Identity would be released from its bondage and he would cast out the inauthentic behaviours which were being expressed.
Unfortunately, as Tharmas did in this passage, mankind often flees from his Identity in pursuit of the Vain Shadow of Hope because his eyes are on Urizen:
Four Zoas, Night VIII, PAGE 122 , (E 383)
"Tharmas on high rode furious thro the afflicted worlds
Pursuing the Vain Shadow of Hope fleeing from identity
In abstract false Expanses that he may not hear the Voice
Of Ahania wailing on the winds in vain he flies for still
The voice incessant calls on all the children of Men
For she spoke of all in heaven & all upon the Earth
Saw not as yet the Divine vision her Eyes are Toward Urizen"