is the one that Dante gives:

"O immaginativa, che ne rube
tal volta si di fuor, ch' uom non s'accorge
perche d'intorno suonin mille tube;

chi move te, se il senso non ti porge?
Moveti lume, che nel ciel s'informa,
per se, o per voler che giu lo scorge.

* * * * *

e qui fu la mia mente si ristretta
dentro da se, che di fuor non venia
cosa che fosse allor da lei recetta."

Certainly, in those moments of exaltation that art can give, it is easy
to believe that we have been possessed by an emotion that comes from the
world of reality. Those who take this view will have to say that there
is in all things the stuff out of which art is made--reality; artists,
even, can grasp it only when they have reduced things to their purest
condition of being--to pure form--unless they be of those who come at it
mysteriously unaided by externals; only in pure form can a sense of it
be expressed. On this hypothesis the peculiarity of the artist would
seem to be that he possesses the power of surely and frequently seizing
reality (generally behind pure form), and the power of expressing his
sense of it, in pure form always. But many people, though they feel the
tremendous significance of form, feel also a cautious dislike for big
words; and "reality" is a very big one. These prefer to say that what
the artist surprises behind form, or seizes by sheer force of
imagination, is the all-pervading rhythm that informs all things; and I
have said that I will never quarrel with that blessed word "rhythm."

The ultimate object of the artist's emotion will remain for ever
uncertain. But, unless we assume that all artists are liars, I think we
must suppose that they do feel an emotion which they can express in
form--and form alone. And note well this further point; artists try to
express emotion, not to make statements about its ultimate or immediate
object. Naturally, if an artist's emotion comes to him from, or through,
the perception of forms and formal relations, he will be apt to express
it in forms derived from those through which it came; but he will not be
bound by his vision. He will be bound by his emotion. Not what he saw,
but only what he felt will necessarily condition his design. Whether the
connection between the forms of a created work and the forms of the
visible universe be patent or obscure, whether it exist or whether it
does not, is a matter of no consequence