ART & SCIENCE

Library of Congress
 Songs of Innocence & of Experience
Plate 9

In his chapter in Blake's Visionary Forms Dramatic W. J. T. Mitchell is presenting his study of Blake's Composite Art: his welding into a single art-form the the arts of poetry and painting. On page 72 he speaks of the role imagination played in Blake's activity:
"But Imagination is not simply a product for Blake, a fixed body of well-defined forms; it is the process by which any symbolic form comes into being. When Blake says he 'copies imagination', he means he renders faithfully the activity of the mind as it alters the objects of perception: both the finished product and the process by which it comes into being are 'imagination.'"

When Blake links Art & Science his aim is to speak of the mental pursuits necessary for building the spiritual dimension in the familiar world in which we live. The Imagination takes intellectual form as Art, physical form as Science. But neither Art nor Science is primarily a product; both are processes through which Imagination, the activity of Eternity, becomes manifest in time and space. Art & Science both exist for the display of 'Naked Beauty'; to make visible through 'forms and features' the lineaments which reveal the underlying Eternal existence.

Jerusalem, Plate 32 [36],(E 179)
"Art & Science cannot exist but by Naked Beauty displayd"

Descriptive Catalogue, (E 544)
"The Beauty proper for sublime art, is lineaments, or
forms and features that are capable of being the receptacles of
intellect;" 

Jerusalem, Plate 77, (E 231)
"Is God a Spirit who must be worshipped in
Spirit & in Truth and are not the Gifts of the Spirit Every-thing
to Man? O ye Religious discountenance every one among
you who shall pretend to despise Art & Science! I call upon you
in the Name of Jesus! What is the Life of Man but Art & Science?
is it Meat & Drink? is not the Body more than Raiment? What is
Mortality but the things relating to the Body, which Dies? What
is Immortality but the things relating to the Spirit, which Lives
Eternally! What is the joy of Heaven but Improvement in the
things of the Spirit? What are the Pains of Hell but Ignorance,
Bodily Lust, Idleness & devastation of the things of the
Spirit[?] 
 Answer this to yourselves, & expel from among you those who
pretend to despise the labours of Art & Science, which alone are
the labours of the Gospel: Is not this plain & manifest to the
thought? Can you think at all & not pronounce heartily! That to
Labour in Knowledge. is to Build up Jerusalem: and to Despise
Knowledge, is to Despise Jerusalem & her Builders. 
  And remember: He who despises & mocks a Mental Gift in another;
calling it pride & selfishness & sin; mocks Jesus the giver of
every Mental Gift, which always appear to the ignorance-loving
Hypocrite, as Sins. but that which is a Sin in the sight of cruel
Man, is not so in the sight of our kind God. 
  Let every Christian as much as in him lies engage himself
openly & publicly before all the World in some Mental pursuit for
the Building up of Jerusalem" 
 
Jerusalem, Plate 52, (E 202)
 "For a Tear is an Intellectual thing;
And a Sigh is the Sword of an Angel King
  And the bitter groan of a Martyrs woe
Is an Arrow from the Almighties Bow!"

Going from the sublime to the mundane, this is the oversimplified understanding of Blake's use of Art & Science as products and process of imagination:
art = mental pursuits = inspired thoughts = poetry and painting,
science = physical pursuits = inspired acts = religion, law and medicine.
.