Gargoyles were the complement to saints; Leonardo's caricatures were complementary to his untiring search for ideal beauty. And gargoyles were the expression of all the passions, the animal forces, the Caliban gruntings and groanings which are left in human nature when the divine has been poured away. Leonardo was less concerned than his Gothic predecessors with the ethereal parts of our nature, and so his caricatures, in their expression of passionate energy, merge imperceptibly into the heroic.

Ch. Three: The Notebooks - Leonardo da Vinci (1939)