For few persons will leave their families, connections, friends, and native land, to seek a settlement in untried foreign climes, without some strong subsisting causes of uneasiness where they are, or the hope of some great advantages in the place to which they are going.
But to make the argument more general and less interrupted by the partial views of emigration, let us take the whole earth, instead of one spot, and suppose that the restraints to population were universally removed.

If the subsistence for man that the earth affords was to be increased every twenty-five years by a quantity equal to what the whole world at present produces, this would allow the power of production in the earth to be absolutely unlimited, and its ratio of increase much greater than we can conceive that any possible exertions of mankind could make it.
Taking the population of the world at any number, a thousand millions, for instance, the human species would increase in the ratio of--1, 2, 4, 8, 16, 32, 64, 128, 256, 512, etc.

and subsistence as--1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.

In two centuries and a quarter, the population would be to the means of subsistence as 512 to 10: in three centuries as 4096 to 13, and in two thousand years the difference would be almost incalculable, though the produce in that time would have increased to an immense extent.
No limits whatever are placed to the productions of the earth; they may increase for ever and be greater than any assignable quantity, yet still the power of population being a power of a superior order, the increase of the human species can only be kept commensurate to the increase of the means of subsistence by the constant operation of the strong law of necessity acting as a check upon the greater power.
The effects of this check remain now to be considered.
Among plants and animals the view of the subject is simple.

They are all impelled by a powerful instinct to the increase of their species, and this instinct is interrupted by no reasoning or doubts about providing for their offspring.