Early-twentieth-century abstraction is art's version of Einstein's Theory of Relativity. It's the idea that changed everything everywhere: quickly decisively for good.

It is not possible to overstate the influence of Paul Cezanne on twentieth-century art. He's the modern Giotto someone who shattered one kind of picture-making and invented a new one that the world followed.

Ads are the cave art of the twentieth century.

All of Koons's best art - the encased vacuum cleaners the stainless-steel Rabbit (the late-twentieth century's signature work of Simulationist sculpture) the amazing gleaming Balloon Dog and the cast-iron re-creation of a Civil War mortar exhibited last month at the Armory - has simultaneously flaunted extreme realism idealism and fantasy.