In general we may observe that the question with regard to the comparative populousness of ages or kingdoms implies very important consequences, and commonly determines concerning the preference of their whole police, their manners, and the constitution of their government. For as there is in all men, both male and female, a desire and power of generation more active than is ever universally exerted, the restraints which they lie under must proceed from some difficulties in their situation, which it belongs to a wise legislature carefully to observe and remove. Almost every man who thinks he can maintain a family will have one, and the human species at this rate of propagation would more than double every generation. How fast do mankind multiply in every colony or new settlement, where it is an easy matter to provide for a family, and where men are nowise straightened or confined as in long established governments? History tells us frequently of plagues which have swept away the third or fourth part of a people; yet in a generation or two the destruction was not perceived, and the society had again acquired their former number. The lands which were cultivated, the houses built, the commodities raised, the riches acquired, enabled the people who escaped immediately to marry and to rear families, which supplied the place of those who had perished.[41] And for a like reason every wise, just, and mild government, by rendering the condition of its subjects easy and secure, will always abound most in people, as well as in commodities and riches. A country, indeed, whose climate and soil are fitted for vines will naturally be more populous than one which is only fitted for pasturage; but if everything else be equal, it seems natural to expect that wherever there are most happiness and virtue and the wisest institutions, there will also be most people.
The question, therefore, concerning the populousness of ancient and modern times being allowed of great importance, it will be requisite, if we would bring it to some determination, to compare both the domestic and political situation of these two periods, in order to judge of the facts by their moral causes, which is the first view in which we proposed to consider them.