INSPIRATION

British Museum
Illustration to Young's Night Thoughts

On page 331 of A Blake Dictionary, Damon points out the quotation of a phrase from Shakespeare's A Midsummer Night's Dream in Blake's Milton. Both men speak of the work of the poet as giving form to the 'airy nothing' which enters the imagination. Blake extends the image beyond the creation of poetry to providing bodies to the Spectres who stand on the threshold of death.
 
Blake pays homage to Shakespeare in this passage by manipulating the words and ideas from Shakespeare and weaving them into his own passage to demonstrate the process of giving shape and habitation to thought, or bodies to Spectres. Blake includes the word 'inspiration' in his passage as indication that the spirit is the active mover in the creation of form. In his annotations to Watson, Blake uses the word 'inspiration' to indicate the difference between writing which purports to be history and 'a poem of probable impossibilities' which is the work of the imagination. 

A Midsummer Night's Dream
Act V, Scene 1
[Theseus speaks]
"The poet's eye, in fine frenzy rolling,
Doth glance from heaven to earth, from earth to heaven;
And as imagination bodies forth
The forms of things unknown, the poet's pen
Turns them to shapes and gives to airy nothing
A local habitation and a name.
Such tricks hath strong imagination,
That if it would but apprehend some joy,
It comprehends some bringer of that joy;
Or in the night, imagining some fear,
How easy is a bush supposed a bear!"

Milton, Plate 28 [30], (E 125)
"Some Sons of Los surround the Passions with porches of iron & silver
Creating form & beauty around the dark regions of sorrow,
Giving to airy nothing a name and a habitation
Delightful! with bounds to the Infinite putting off the Indefinite
Into most holy forms of Thought: (such is the power of inspiration)
They labour incessant; with many tears & afflictions:
Creating the beautiful House for the piteous sufferer.

Others; Cabinets richly fabricate of gold & ivory;
For Doubts & fears unform'd & wretched & melancholy
The little weeping Spectre stands on the threshold of Death      
Eternal; and sometimes two Spectres like lamps quivering
And often malignant they combat (heart-breaking sorrowful & piteous)
Antamon takes them into his beautiful flexible hands,
As the Sower takes the seed, or as the Artist his clay
Or fine wax, to mould artful a model for golden ornaments,      
The soft hands of Antamon draw the indelible line:
Form immortal with golden pen; such as the Spectre admiring
Puts on the sweet form;" 

Annotations to Watson, (E 616)
 "He who writes things for true which none could write. but
the actor. such are most of the acts of Moses. must either be the
actor or a fable writer or a liar.  If Moses did not write the
history of his acts, it takes away the authority altogether it
ceases to be history & becomes a Poem of probable impossibilities
fabricated for pleasure as moderns say but I say by Inspiration."