What was the nature of the revolution in the manner of laying out a new town associated with the name of Hippodamos of Miletus? Aristotle suggests that it was simply a matter of regularity. The old way was to build irregularly, the new way to build regularly after the manner invented by Hippodamos. If this is true, how came it that the regular manner was adopted, presumably, in the first half of the fifth century? What movement of ideas brought it into favour? To what special circumstances did it constitute a response? Why had it not developed earlier as an obvious consequence, for instance, of the founding of new cities in the great age of Greek colonisation? And if the new colonial cities of the eighth, seventh and sixth centuries were not planned in a regular fashion, how were they planned?