Flaubert on How to Judge a Work of Art

While doing our readaloud on Madame Bovary, I'm also flipping through the pages of Flaubert's letters:

What seems to me the highest and most difficult achievement of Art is not to make us laugh or cry, or to rouse our lust or our anger but to do as nature does--that is, fill us with wonderment.  The most beautiful works have indeed this quality.  They are serene in aspect, incomprehensible.  The means by which they act on us are various: they are as unmoving as cliffs, stormy as the ocean, leafy, green,and murmuring as forests, sad as the desert, blue as the sky. Homer, Rabelais, Michelangelo, Shakespeare and Goethe seem to me pitiless.  They are bottomless, infinite, multiple.  Through small openings we glimpse abysses whose dark depths make us giddy.  And yet over the whole there hovers an extraordinary gentleness.   It is like the brilliance of light, the smile of the sun, and it is calm, calm, and strong. ...

That's from a letter to Louise Colet, dated "Friday night, 11 o'clock," --from Trouville, August 26, 1853.   See Selected Letters of Gustave Flaubert (Francis Steegmuller ed.)  161 (1953).  One surmises that this is the standard by which he would wish his own work, or at least Bovary, to be judged.