In the 1960's, when the world was flat, everything had its order - there was still a working class with whom bourgeois intellectuals could identify and a bourgeoisie to be provoked and shocked. In those more simple years artists could rouse the police to action by simply taking off their clothes or doing strange things with dead sheep. But by the 1970's the shape of the world had changed. Television had shown us men on the moon waving flags and golf clubs - suburban America had arrived in space and sent back images of a small, blue, round planet. Flatness (colour-field painting, drive-in cinemas, perspective, history), began to go out of style and by the 1980's McLuhan's predictions of globality were being dusted off and recycled first as post-modernism (in spite of its nostalgia for the flatness of Mussolini's politics and architecture) and then as post-industrialism, post-rationalism and finally, with the collapse of the socialist planned economies, post-humanism.

In the old flat world of the 60's awkward ideas and non-consumerist societies could be pushed, if not exactly off the edge of the planet, at least to its perimeter. But McLuhan's spherical world has, notoriously, no perimeters or edges - or even centres - all that really matters are connections and the spaces between. Dominant industrial societies and what is left of the old art-world, long accustomed to perceiving themselves to be at the centre of a disk, are now obliged to share the surface of a globe with all kinds of art and ideas and cultures that were thought to be safely on the rim.

500 years after Columbus' famous voyage it is finally becoming clear that flat-earth thinking - edges, centres, corners, straight lines - is not very useful in a spherical world where speed-of-light technology and communications makes everything happen everywhere at the same time.