The concern is that the images to be devised won't be sufficiently upsetting: not concrete, not detailed enough. Pity can entail a moral judgement if, as Aristotle maintains, pity is considered to be the emotion that we owe only to those enduring undeserved misfortune. But pity, far from being the natural twin of fear in the dramas of catastrophic misfortune, seems diluted—distracted—by fear, while fear (dread, terror) usually manages to swamp pity. Leonardo is suggesting that the artist's gaze be, literally, pitiless. The image should appall, and in that terribilità lies a challenging kind of beauty.

Susan Sontag