"All things are in a state of constant flux; the fire of God descends through the air and water to earth, and reascends from water and air to its 'fire-source'".
We may take these to be the four zoas. In the interaction between the four we have birth and death, or death and birth as you please. Blake's myth may be stated as going from Eternity to a watery Earth; it may be called the Sea of Time and Space.
Blake related this process to the alchemical one.
The alchemical procedure was to put base metals in the crucible and apply fire, hoping to come out with gold.
(In a corresponding way Blake used the furnace of Los to form our bodies:
From Urizen, Erdman 75:
"Forgetfulness, dumbness, necessity!
in chains of the mind locked up,
Like fetters of ice shrinking together
Disorganiz'd, rent from Eternity,
Los beat on his fetters of iron;
And heated his furnaces & pour'd
Iron sodor and sodor of brass"
(Hoping to produce gold!)
From Night 2 of The Four Zoas (erdman 317):
"Luvah was cast into the Furnaces of affliction & sealed
And Vala fed in cruel delight, the furnaces with fire
Stern Urizen beheld urg'd by necessity to keep
The evil day afar, & if perchance with iron power
He might avert his own despair; in woe & fear he saw"
and many others.
Blake broadly spoke of the furnaces of affliction in which
we are all involved. We are said to fall from Heaven to
Beulah, sleeping there we fall to Ulro. In the furnace of
afflictions we're generated and and in course of time
regenerated or reborn.
Death to Blake was a liberation of the reborn into the Heaven from which