Blake's Jerusalem begins with a memorable image of Los entering the dark doorway of a crypt carrying in his hand a light to illuminate his steps. The ideas contained in the post CONSUMED IN FIRE follow from the concepts incorporated in the image and legend in this frontispiece. The 'Door of death' which Los enters is to the world which we call life. Entering the physical world is experienced as Death to eternity. Reentering eternity is experienced as death to the world. In the Gospels Jesus had this to say:
 Whosoever shall seek to save his life shall lose it; and whosoever shall lose his life shall preserve it.
 He that loveth his life shall lose it; and he that hateth his life in this world shall keep it unto life eternal.
Minna Doskow's book Jerusalem: Structure and Meaning in Poetry and Picture analyzes the text and illustrations of Jerusalem. Also included is a facsimile of Blake's book which facilitates the study of both facets of Blake's communication. She writes this about the initial plate of Jerusalem:
"The full-page illustration of Los entering 'the Door of Death for Albion's sake Inspired' (1:19) with which Jerusalem opens captures the situation of the whole poem in the image of a single action, a single figure, and a single moment. From the graffiti over the doorway, we learn of the two adjacent, coexistent, and omnipresent realms the the poem explores - the Void (also called sleep, Ulro, or Generation in the poem) and Existence (alternatively called awakening, Eden, or Eternity). While the poem tells us much about the meaning of these two realms, this plate immediately gives us their salient features. Existence is characterized by the imaginative light pictured in the illustration, while the Void is poetically described by sleep, shadow and rock (1:3-4). Albion's initial position is in the void, dead, with petrified and 'fixed' intellect and emotions (his 'sublime' and 'pathetic' qualities [1:4]), enclosed by limited reason (his covering 'Spectrous Power' [1:5]), which does not allow him to see further than this fallen universe that he creates and is limited to (1:1-2)." (Page 26)
Jerusalem, Title Page, (E 144)
The Emanation of The Giant Albion
1804 Printed by W. Blake Sth Molton St.
[The following text is not visible in this copy of the plate but readable on other copies.]
[Above the archway:]
"There is a Void, outside of Existence, which if enterd into
Englobes itself & becomes a Womb, such was Albions Couch
A pleasant Shadow of Repose calld Albions lovely Land
His Sublime & Pathos become Two Rocks fixd in the Earth
His Reason his Spectrous Power, covers them above
Jerusalem his Emanation is a Stone laying beneath
O [Albion behold Pitying] behold the Vision of Albion
[On right side of archway:]
Half Friendship is the bitterest Enmity said Los
As he enterd the Door of Death for Albions sake Inspired
The long sufferings of God are not for ever there is a Judgment
[On left side, in reversed writing:]
Every Thing has its Vermin O Spectre of the Sleeping Dead"
As Doskow implies, she and Blake both wrote their books to 'contrast between sleep in Ulro (Albion's fallen state) and the awakened Eternal Life (the Savior's unified state of identity and mutual love between man and God) [which] could not become more complete than it is at the outset.' (Page 16)
It is all about changing sleep to awakening, death to life, Ulro to Eternity.