Yet the importance of the Pre-Socratics thinkers lies less in their influence - great though that was - than in their astonishing intellectual ambition and imaginative reach.

Zeno's dizzying 'proofs' that motion is impossible; the extraordinary atomic theories of Democritus; the haunting and enigmatic epigrams of Heraclitus; and the maxims of Alcmaeon: fragmentary as they often are, the thoughts of these philosophers seem strikingly modern in their concern to forge a truly scientific vocabulary and way of reasoning.