ETERNAL DEED

Why should those who exist at a level of development higher than the turmoil of the world we know concern themselves with our petty concerns? Why not remain aloof in the ever-fluctuating world of mental delights. An awareness of an aberration comes into their field of perception: one of their own has assumed a limitation and entered a state.   

Jerusalem, Plate 55, (E 204)
"When those who disregard all Mortal Things, saw a Mighty-One
Among the Flowers of Beulah still retain his awful strength
They wonderd; checking their wild flames & Many gathering
Together into an Assembly; they said, let us go down
And see these changes! Others said, If you do so prepare         
For being drived from our fields, what have we to do with the Dead?
To be their inferiors or superiors we equally abhor;
Superior, none we know: inferior none: all equal share
Divine Benevolence & joy, for the Eternal Man
Walketh among us, calling us his Brothers & his Friends:         
Forbidding us that Veil which Satan puts between Eve & Adam
By which the Princes of the Dead enslave their Votaries
Teaching them to form the Serpent of precious stones & gold
To sieze the Sons of Jerusalem & plant them in One Mans Loins
To make One Family of Contraries: that Joseph may be sold        
Into Egypt: for Negation; a Veil the Saviour born & dying rends."

Consensus was destroyed among the Immortals: some drew back, some choose to explore. The spark had ignited the evolution of consciousness which resulted from the initiation of duality in the form of the 'Family of Contraries.'  Blake provides no fanfare for the event that shook the universe, saying only: "Let us to him who only Is, & who Walketh among us, give decision." Apparently the situation is controlled by the word 'Is' as representing a level of existence other than that of the Eternals, which has become an option that may be entered.

"But others said: Let us to him who only Is, & who
Walketh among us, give decision. bring forth all your fires!

So saying, an eternal deed was done: in fiery flames

The Universal Conc[l]ave raged, such thunderous sounds as never
Were sounded from a mortal cloud, nor on Mount Sinai old
Nor in Havilah where the Cherub rolld his redounding flame.

Loud! loud! the Mountains lifted up their voices, loud the Forests
Rivers thunderd against their banks, loud Winds furious fought
Cities & Nations contended in fires & clouds & tempests.         
The Seas raisd up their voices & lifted their hands on high
The Stars in their courses fought. the Sun! Moon! Heaven! Earth.
Contending for Albion & for Jerusalem his Emanation
And for Shiloh, the Emanation of France & for lovely Vala.

Then far the greatest number were about to make a Separation"  

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Milton's Paradise Lost

Satan Calling Up His Legions

Milton's war in heaven which in Paradise Lost, led to the creation of our world resulted from the pride of Lucifer and his fear of being supplanted by the creation of mankind. Blake's fall was simply a separation: a movement to walk among those who had entered temporal existence.