“For it pertains to the statesman to know how large a city should be and whether it should include men of one nation or of several. The size of the city should indeed be such that the region may be sufficiently productive and that it may be possible to repel external enemies. It should also preferably be made up of a single nation in view of the fact that the men of the same nation possess the same way of life and the same customs, which foster friendship among the citizens because of their resemblance. Accordingly, the cities that were constituted out of different nations were ruined on account of the dissensions that arose in them due to the diversity of manners, for one part used to ally itself with [external] enemies out of hatred for the other part.”