It is often said that Leonardo drew so well because he knew about things; it is truer to say that he knew about things because he drew so well.

The history of art cannot be properly understood without some reference to the history of science. In both we are studying the symbols by which man affirms his mental scheme, and these symbols, be they pictorial or mathematical, a fable or formula, will reflect the same changes.

Racial prejudices are indication of a disturbed and potentially unstable society.

Great works of art can be produced in barbarous societies - in fact the very narrowness of primitive society gives their ornamental art a peculiar concentration and vitality. At some time in the ninth century one could have looked down the Seine and seen the prow of a Viking ship coming up the river. Looked at today in the British Museum, it is a powerful work of art; but to the mother of a family trying to settle down in her little hut, it would have seemed less agreeable - as menacing to her civilisation as the periscope of a nuclear submarine.

The eye instinctively looks for analogies and amplifies them, so that a face imagined in the pattern of a wallpaper may become more vivid than a photograph.

Those who wish, in the interest of morality, to reduce Leonardo, that inexhaustible source of creative power, to a neutral or sexless agency, have a strange idea of doing service to his reputation.

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.