All poetry, being a species of painting, brings us nearer to the objects than any other species of narration, throws a stronger light upon them, and delineates more distinctly those minute circumstances which, though to the historian they seem superfluous, serve mightily to enliven the imagery and gratify the fancy.
The claim that poetry is a species of painting is an allusion to a famous line by Horace: Ut pictura poesis (as with painting, so with poetry). It's found in the Ars Poetica:
Ut pictura poesis; erit quae, si propius stes,
te capiat magis, et quaedam, si longius abstes;
haec amat obscurum, uolet haec sub luce uideri,
iudicis argutum quae non formidat acumen;
haec placuit semel, haec deciens repetita placebit.
Here's a decent enough transmogrification into English rhyme:
Poems like pictures are; some charm when nigh,
Others at distance more delight your eye;
That loves the shade, this tempts a stronger light,
And challenges the critic's piercing sight:
That gives us pleasure for a single view;
And this, ten times repeated, still is new.
The analogy has influenced an immense amount of aesthetics, and did so particularly in the early modern period. (As I think Gilson notes, Horace's actual statement doesn't license any analogy between poetry and painting as arts; it's an analogy between reading of poetry and viewing of paintings -- that is, it is an analogy between the artistic criticism applicable to poetry and the artistic criticism applicable to painting. Some poems are to be read closely, some from afar; some look better in the shade, some under piercing examination; some are best as single shots, and some you can read again and again. But this is usually overlooked, and the analogy is taken to be between the arts.)
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