The first of these limitations was the obsession of the Greek mind by the idea of the city as the ultimate state. In a world in which empire had followed empire, each greater than its predecessor, in a world through which men and ideas drove ever more loosely and freely, in a world visibly unifying even then, the Greeks, because of their peculiar physical and political circumstances, were still dreaming impossibly of a compact little city state, impervious to outer influences, valiantly secure against the whole world. Plato’s estimate of the number of citizens in a perfect state varied between 1000 (the _Republic_) and 5040 (the _Laws_) citizens.[194] This state was to go to war and hold its own against other cities of the same size. And this was not a couple of generations after the hosts of Xerxes had crossed the Hellespont! Perhaps these Greeks thought the day of world empires had passed for ever, whereas it was only beginning. At the utmost their minds reached out to alliances and leagues. There must have been men at the court of Artaxerxes thinking far away beyond these little ideas of the rocky creek, the island, and the mountain-encircled valley. But the need for unification against the greater powers that moved outside the Greek-speaking world, the Greek mind disregarded wilfully. These outsiders were barbarians, not to be needlessly thought about; they were barred out now from Greece for ever. One took Persian money; everybody took Persian money; what did it matter? Or one enlisted for a time in their armies (as Xenophon did) and hoped for his luck with a rich prisoner. Athens took sides in Egyptian affairs, and carried on minor wars with Persia, but there was no conception of a common policy or a common future for Greece.... Until at last a voice in Athens began to shout “Macedonia!” to clamour like a watch-dog, “Macedonia!” This was the voice of the orator and demagogue Demosthenes, hurling warnings and threats and denunciations at King Philip of Macedon, who had learnt his politics not only from Plato and Aristotle, but also from Isocrates and Xenophon, and from Babylon and Susa, and who was preparing quietly, ably, and steadfastly to dominate all Greece, and through Greece to conquer the known world....