The various parts of the body cannot be perceived as simple units and have no clear relationship to one another. In almost every detail the body is not the shape that art has led us to believe it should be.

Almost all great painters in old age arrive at the same kind of broad, simplified style, as if they wanted to summarise the whole of their experience in a few strokes and blobs of colour.

Fine colour implies a unified relationship, in which each part is subordinate to the whole, and the transitions between them are felt to be as precious and beautiful as the colours themselves. In fact, the colours themselves must be continuously modified and broken as part of the transition.

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.

However much the various phases of the French Revolution may have modelled themselves on Roman history the early phase on Republican virtue, the later on Imperial grandeur the fact remains that classicism depended on a fixed and rational philosophy; whereas the spirit of the Revolution was one of change and of emotion.

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.

Only the bad artists of the nineteenth century were frightened by the invention of photography; the good ones all welcomed it and used it. Degas liked it not only because it provided an accurate record, but because the snapshot showed him a means of escape from the classical rules of design. Through it he learnt to make a composition without the use of formal symmetry.