Three distinct facts--preventive restraint, vice, and misery--having nothing else in common, are arranged under one general head by Malthus, in consequence of the one single common property which they possess--that of operating as checks to population. To him, that one common property was the most important of all, and the most fit to be singled out as the groundwork of classification, having reference to the subject of his enquiry. But Plato and Aristotle looked at the subject in a different point of view. They had present to their minds the same three facts, and the tendency of the first to avert or abate the second and third: but as they were not investigating the law of population, they had nothing to call their attention to the one common property of the three. They did not regard vice and misery as causes tending to keep down population, but as being in themselves evils; enemies among the worst which the lawgiver had to encounter, in his efforts to establish a good political and social condition--and enemies which he could never successfully encounter, without regulating the number of births. Such regulation they considered as an essential tutelary measure to keep out disastrous poverty. The inverse proportion, between regulated or unregulated number of births on the one hand, and diminution or increase of poverty on the other, was seen as clearly by Aristotle and Plato as by Malthus. [Side-note: Regulations of Plato and Aristotle as to number of births and newborn children.] But these two Greek philosophers ordain something yet more remarkable. Having prescribed both the age of marriage and the number of permitted births, so as to ensure both vigorous citizens and a total compatible with the absence of corrupting poverty--they direct what shall be done if the result does not correspond to their orders. Plato in his Republic (as I have already stated) commands that all the children born to his wedded couples shall be immediately consigned to the care of public nurses--that the offspring of the well-constituted parents shall be brought up, that of the ill-constituted parents not brought up--and that no children born of parents after the legitimate age shall be brought up.[171] Aristotle forbids the exposure of children, wherever the habits of the community are adverse to it: but if after any married couple have had the number of children allowed by law, the wife should again become pregnant, he directs that abortion shall be procured before the commencement of life or sense in the foetus: after such commencement, he pronounces abortion to be wrong.[172] On another point Plato and Aristotle agree: both of them command that no child born crippled or deformed shall be brought up:[173] a practice actually adopted at Sparta under the Lykurgean institutions, and even carried farther, since no child was allowed to be brought up until it had been inspected and approved by the public nurses.[174]