It is either Delacroix or Baudelaire who wrote: "The writer who is incapable of saying everything, who takes unawares and without having enough material to give body to an idea, however subtle or strange or unexpected he may suppose it to be, is not a writer." And one has to beware of the sin of allegory, which spoils even Bunyan's prose. For the deepest emotion raised in us by allegory is a very imperfectly satisfied sense of the writer's ingenuity in overcoming a difficulty we should have preferred his not having attempted to overcome.
Then there is the heresy of instruction--_l'hérésie de l'enseignement_--which Poe and Baudelaire and Swinburne consider ruinous to art. Art for art's sake first of all; that a poem must be written for the poem's sake simply, from whatever instinct we have derived it; it matters nothing whether this be inspired by a prescient ecstasy of the beauty beyond the grave, or by some of that loveliness whose very elements appertain solely to eternity. Above all, Verlaine's _Pas de couleur, rien que la nuance!_
The old war--not (as some would foolishly have it defined) a war between facts and fancies, reason and romance, poetry and good sense, but simply between imagination which apprehends the spirit of a thing and the understanding which dissects the body of a fact--the strife which can never be decided--was for Blake the most important question possible. Poetry or art based on loyalty to science is exactly as absurd (and no more) as science guided by art or poetry. Though, indeed, Blake wrought his _Marriage of Heaven and Hell_ into a form of absolute magnificence, a prose fantasy full of splendid masculine thought and of a diabolical or infernal humour, in which hells and heavens change names and alternate through mutual annihilations, which emit an illuminating, devouring, and unquenchable flame, he never actually attained the incomparable power of condensing vapour into tangible and malleable form, of helping us to handle air and measure mist, which is so instantly perceptible in Balzac's genius, he who was not "a prose Shakespeare" merely, but rather perhaps a Shakespeare in all but the lyrical faculty.
Even when Baudelaire expresses his horror of life, of how abject the world has become, how he himself is supposed to be "une anomalie," his sense of his own superiority never leaves him. "Accursed," as I have said, such abnormally gifted artists are, he declares his thirst of glory, a diabolical thirst of fame and of all kinds of enjoyments--in spite of his "awful temperament, all ruse and violence"--and can say: "I desire to live and to have self-content. Something terrible says to me _never,_ and some other thing says to me _try. Moi-même, le boulevard m'effraye_."