On the other hand, the laws even of Sparta, framed with a view to the military strength of the State considered as the small free population, were ultimately evaded in the interests of property-holding, till the number of "pure Spartans" dwindled to a handful.[241] Under a system of primogeniture, with a rigid severance between the upper class and the lower, there could in fact be no other outcome. Here, apart from the revolts of the helots and the chronic massacres of these by their lords, which put such a stamp of atrocity on Spartan history,[242] the stress of class strife seems to have been limited among the aristocracy, not only by systematic infanticide, but by the survival of polyandry, several brothers often having one wife in common.[243] Whether owing to infanticide, or to in-breeding, or to preventives, families of three and four were uncommon and considered large, and special privileges offered to the fathers.[244] As always, such devices failed against the pressures of the main social conditions. All the while, of course, the _perioikoi_ and the enslaved helots multiplied freely; hence the policy of specially thinning down the latter by over-toil[245] as well as massacre. In other States, where the polity was more civilised, many observers perceived that the two essential conditions of stability were (_a_) absolute or approximate equality of property, and (_b_) restraint of population, the latter principle being a notable reaction of reason against the normal practice of encouraging or compelling marriage.[246] Aristotle said in so many words that to let procreation go unchecked "is to bring certain poverty on the citizens; and poverty is the cause of sedition and evil";[247] and he cites previous publicists who had sought to solve the problem. Socrates and Plato had partly contemplated it; and the idealist, as usual, had proposed the more brutal methods;[248] but Aristotle, seeing more clearly the population difficulty, perhaps on that account is the less disposed towards communism.