You have abundantly proved, that natural fecundity is hardly to be considered, because the vis generandi, as far as we know, is unlimited, and because experience shows, that the numbers of nations is altogether governed by collateral causes, and among these none of so much force as quantity of subsistence, whether arising from climate, soil, improvement of tillage, trade, fisheries, secure property, conquest of new countries, or other favourable circumstances.
As I perfectly concurred with you in your sentiments on these heads, I have been very desirous of building somewhat on the foundation you have there laid; and was induced, by your hints in the twenty-first section, to trouble you with some thoughts on the influence manners have always had, and are always likely to have, on the numbers of a people, and their political prosperity in general.
The end of every individual is its own private good. The rules it observes in the pursuit of this good are a system of propositions, almost every one founded in authority, that is, derive their weight from the credit given to one or more persons, and not from demonstration.
And this, in the most important as well as the other affairs of life, is the case even of the wisest and philosophical part of the human species; and that it should be so is the less strange, when we consider, that it is perhaps impossible to prove, that being, or life itself, has any other value than what is set on it by authority.
A confirmation of this may be derived from the observation, that, in every country in the universe, happiness is sought upon a different plan; and, even in the same country, we see it placed by different ages, professions, and ranks of men, in the attainment of enjoyments utterly unlike.
These propositions, as well as others framed upon them, become habitual by degrees, and, as they govern the determination of the will, I call them moral habits.
There are another set of habits, that have the direction of the members of the body, that I call therefore mechanical habits. These compose what we commonly call the arts, which are more or less liberal or mechanical, as they more or less partake of assistance from the operations of the mind.
The cumulus of the moral habits of each individual is the manners of that individual; the cumulus of the manners of individuals makes up the manners of a nation.
The happiness of individuals is evidently the end of political society; and political welfare, or the strength, splendour, and opulence of the state, have been always admitted, both by political writers, and the valuable part of mankind in general, to conduce to this end, and are therefore desirable.