Thirlwall, in his closing survey, proceeding on Polybius,[249] confidently decides that the main cause of depopulation was domestic and moral. Such a theory cannot be sustained. Polybius evidently had no clear idea of the facts, since he asserts that "in our time" and "rapidly" there took place in Greece a "failure of offspring" (or "dearth of children"), which left cities desolate and land waste; and goes on to ascribe it to habits of luxury, which either kept men from marrying or made them refuse to rear more than a few of their children. The whole theorem is haphazard. Cities and lands could not have been so depopulated.[250] There must have been, in addition to slaughter, a drain of population to lands where the conditions were more advantageous. Nor is there any good reason for believing that child-exposure had suddenly and immensely increased. Thirlwall says that marriages were "unfruitful"; but this is not the statement of Polybius. It is true that pæderasty would count for much in lowering character; but it had been common in Greece centuries before the time of Polybius, and had not affected fecundity. As we have seen,[251] fecundity fell in Sparta for other reasons. As between Sparta and Athens, the main difference was that Athenian life was for a long period more or less expansive, while that of Sparta, even in the period of special vigour, was steadily contractive, as regarded quantity and quality of "good life." At Sparta, as above noted, the normal play of self-interest in the governing class brought about a continuous shrinkage in the number of enfranchised citizens and of those holding land, till there were only 700 of the former and 100 of the latter--this when there were still 4,500 adult Spartans of "pure" descent, and 15,000 Laconians capable of military service. Even of the hundred landowners many were women, the estates having thus evidently aggregated by descent through heiresses.[252] It mattered little that this inner ring of rich became, after the triumph over Athens and in the post-Alexandrian period, as luxurious as the rest of Greece:[253] the evil lay not in the mode of their expenditure, but in the mode of their revenue. Agis IV and his successor Cleomenes thought to put the community on a sound footing by abolition of debts and forcible division of the land; but even had Agis triumphed at home or Cleomenes maintained himself abroad, the expedient could have availed only for a time. Accumulation would instantly recommence in the absence of a scientific and permanent system.