[Side-note: Law of population expounded by Malthus--Three distinct checks to population--alternative open between preventive and positive.] The first of these three purposes is peculiar to the Platonic system. The two last are not peculiar to it. Aristotle recognises them[162] as ends, no less than Plato, though he does not approve Plato's means for attaining them. In reference to the limitation of number, Aristotle is even more pronounced than Plato. The great evil of over-population forced itself upon these philosophers; living as both of them did among small communities, each with its narrow area hedged in by others--each liable to intestine dispute, sometimes caused, always aggravated, by the presence of large families and numerous poor freemen--and each importing bought slaves as labourers. To obtain for their community the quickest possible increase in aggregate wealth and population, was an end which they did not account either desirable or commendable. The stationary state, far from appearing repulsive or discouraging, was what they looked upon as the best arrangement[163] of things. A mixed number of lots of land, indivisible and inalienable, is the first principle of the Platonic community in the treatise De Legibus. Not to encourage wealth, but to avert, as far as possible, the evils of poverty and dependence, and to restrain within narrow limits the proportion of the population which suffered those evils--was considered by Plato and Aristotle to be among the gravest problems for the solution of the statesman.[164] Consistent with these conditions, essential to security and tranquillity, whatever the form of government might be, there was only room for the free population then existing: not always for that (seeing that the proportion of poor citizens was often uncomfortably great), and never for any sensible increase above that. If all the children were born and brought up, that it was possible for adult couples to produce, a fearful aggravation of poverty, with all its accompanying public troubles and sufferings, would have been inevitable.[165] Accordingly both Plato (for the Guardians in the Republic) and Aristotle agree in opinion that a limit must be fixed upon the number of children which each couple is permitted to introduce. If any objector had argued that each couple, by going through the solemnity of marriage, acquired a natural right to produce as many children as they could, and that others were under a natural obligation to support those children--both philosophers would have denied the plea altogether. But they went even further. They considered procreation as a duty which each citizen owed to the public, in order that the total of citizens might not fall below the proper minimum--yet as a duty which required controul, in order that the total might not rise above the proper maximum.[166] Hence they did not even admit the right of each couple to produce as many children as their private means could support.