'The most beautiful object is the one that does not exist', writes the Polish poet Zbigniew Herbert. His phrase is paradoxical and suggestive: the beautiful object in question may be the Platonic form we never encounter directly in reality; it may even - whimsical thought - be the product the Polish consumer never sees in the shops. In any case, it is privileged because it stimulates the imagination, the faculty which - ever since Romanticism, and Coleridge's formulation of the distinction between Imagination and Fancy - has been a primary organ of our perception of the world. Imagination was granted this role because of its capacity to conquer distance: in the early nineteenth century, as the world begins to shrink beneath the tightening embrace of new transport and communications systems, Imagination provides advance notice of imminent new realities. It permits one to domesticate the shock of the new, of the other cultures imported into one's own by the linked processes of industrialization and colonialism. Imagination generates an art of prophecy: it renders the trembling of the rails in advance of the coming train. It introduces into the present a negative object (the temporal ghost of the flash-forward to an object) that will shortly negate one itself through its real presence. It converts this object into a phantom, a figure of dread or desire, so that on arrival it will pass spectrally through the perceiver, unhindered by his or her material presence or frictional resistance. It anticipates the future in ...