Leonardo is the Hamlet of art history whom each of us must recreate for himself.

Few people can look at a painting longer than it takes to peel an orange and eat it.

Our universe cannot even be stated symbolically. And this touches us all more directly than one might suppose. For example, artists, who have been very little influenced by social systems, have always responded instinctively to latent assumptions about the shape of the universe. The incomprehensibility of our new cosmos seems to me, ultimately, to be the reason for the chaos of modern art.

It would be unfair to say that I prefer the back of a book to its contents, but it is true that the sight of a lot of books gives me the hope that I may some day read them, which sometimes develops into the belief that I have read them.

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.

Ruskin's much-derided moral theory of art was part of an attempt to show that this human activity, which we value so highly, engaged the whole of human personality. His insistence on the sanctity of nature was part of an attempt to develop Goethe's intuition that form cannot be put together in the mind by an additive process, but is to be deduced from the laws of growth in living organisms, and their resistance to the elements.

I believe in courtesy, the ritual by which we avoid hurting other people's feelings by satisfying our own egos.