In the Leonardo da Vinci's sketches, many parts are lost in obscurity, or are left intentionally uncertain and mysterious, even in the light, and you might at first imagine some permission of escape had been here given you from the terrible law of delineation. But the slightest attempts to copy them will show you that the terminal lines are inimitably subtle, un-accusably true, and filled by gradations of shade so determined and measured that the addition of a grain of lead or chalk as large as the filament of a moth's wing would make an appreciable difference in them.
There may not be in the world another example of a genius so universal, so inventive, so incapable of fulfillment, so full of yearning for the infinite, so naturally refined, so far ahead of his own century and the following centuries. Leonardo da Vinci's figures reveal an incredible sensitivity and intellect; they are full of unexpressed ideas and feelings. Next to them, Michelangelo's David is mere a heroic athlete, Raphael's Sistine Madonna only placid girl whose un-awakened soul has never know life. Leonardo's portraits feel and think through every feature and every expression; it takes some time to establish a dialogue with them; not that their feeling is not clear enough, on the contrary it bursts out of the whole figure, but it is too subtle, too complicated, too much outside and beyond ordinary experience, too unfathomable, too unexplainable. Their immobility and their silence allow us to guess two or three layers of thought and other deeper thoughts, hiding behind the most remote layer; we vaguely discern this intimate, secret world, like a delicate, unknown vegetation below the depths of a transparent water.