I just stepped out of the dark, still forest and found myself on a rising hill. In front of me I saw a valley, surrounded by fertile hills, in which … - Caspar David Friedrich

It is doubtful whether the artist [unknown] altogether knew what he depicted here in this panel, and even more doubtful whether he could have expressed it in words. That which we praise here as well thought-out and cleverly arranged may, in fact, have been achieved by him unconsciously; for the artist was transformed by pure harmoniousness while executing this picture, and his feeling become his law. Only his disposition, his spiritual exaltation, could have brought forth such a fruit as this picture. Just as the pious man prays without speaking a word and the Almighty hearkens unto him, so the artist with true feeling paints and the sensitive man understands and recognizes it; while even the less sensitive gain some inkling of it.

Why, it has often occurred to me to ask myself, do I so frequently choose death, transience, and the grave as subjects for my paintings? One must submit oneself many times to death in order some day to attain life everlasting.

If a painting has a soulful effect on the viewer, if it puts his mind into a soulful mood, then it has fulfilled the first requirement of a work of art. However bad it might be in drawing, color, handling, etc.