The great law of necessity which prevents population from increasing in any country beyond the food which it can either produce or acquire, is a law so open to our view, so obvious and evident to our understandings, and so completely confirmed by the experience of every age, that we cannot for a moment doubt it.

The different modes which nature takes to prevent or repress a redundant population do not appear, indeed, to us so certain and regular, but though we cannot always predict the mode we may with certainty predict the fact.

If the proportion of births to deaths for a few years indicate an increase of numbers much beyond the proportional increased or acquired produce of the country, we may be perfectly certain that unless an emigration takes place, the deaths will shortly exceed the births; and that the increase that had taken place for a few years cannot be the real average increase of the population of the country.
Were there no other depopulating causes, every country would, without doubt, be subject to periodical pestilences or famine.
The only true criterion of a real and permanent increase in the population of any country is the increase of the means of subsistence.
But even, this criterion is subject to some slight variations which are, however, completely open to our view and observations.

In some countries population appears to have been forced, that is, the people have been habituated by degrees to live almost upon the smallest possible quantity of food.

There must have been periods in such counties when population increased permanently, without an increase in the means of subsistence.