The _jus trium liberorum_, and the other encouragements given by Augustus Cæsar to engage the Romans to marry, were calculated chiefly for the nobility, and only for the citizens, but not at all for the inferior class (the slaves) bound to labour. The vice to be corrected, and that which the emperor had in his eye in those institutions, was the prodigal and dissolute life of rich men who lived in celibacy. This affected the Roman state, and deprived it of its principal force, the military power, the equites. Judge of the force of this class by the numbers of them destroyed at Cannæ. In those days, the chief encouragement to multiplication was to be directed towards the higher classes; the lower classes of the people (by far the most numerous in all countries and in all ages) were easily recruited, by the importation of slaves, as they are now in the West-Indies, where, consequently, the same principle must naturally operate, which fixed the attention of the wise emperor. The state of affairs in Europe, and in England particularly, is changed entirely, by the establishment of universal liberty. Our lowest classes are absolutely free; they belong to themselves, and must bring up their own children, else the state becomes depopulated. There is no resource to us from importation, whether by ships, or acts of parliament for naturalization. We shall always have a numerous and free common people, and shall constantly have the same inconveniencies to struggle with, as long as the lowest classes remain in such depression as not to be able to support their own numbers. Here then lies the difficulty. In order to have a flourishing state, which Sir William Temple beautifully compared to a pyramid, we must form a large and solid basis of the lowest classes of mankind. As the classes mount in wealth, the pyramid draws narrower until it terminate in a point, (as in monarchy) or in a small square, as in the aristocratical and mixed governments. This lowest class therefore must be kept up, and, as we have said, by its own multiplication. But where every one lives by his own industry, a competition comes in, and he who works cheapest gains the preference. How can a married man, who has children to maintain, dispute this preference with one that is single? The unmarried therefore force the others to starve; and the basis of the pyramid is contracted. Let this short sketch of a most important part of our subject suffice at present; it shall be taken up and examined at more length, in the chapter of physical necessaries, or natural wants. From this results the principal cause of decay in modern states: it results from liberty, and is inseparably connected with it.