In 1860, sixty-three per cent of the couples married in Great Britain had families of four or more children; in 1925 only twenty per cent had more than four.

Population, when unchecked, goes on doubling itself every 25 years or increases in a geometrical ratio.

To prevent the recurrence of misery is, alas! beyond the power of man.

The first business of philosophy is to account for things as they are; and till our theories will do this, they ought not to be the ground of any practical conclusion.

Population trends have always provoked doom-fraught oracles, because their popular interpreters suppose that every new series will be infinitely sustained; yet, beyond the short term, expectations based on them are never fulfilled.

Subsistence increases only in an arithmetical ratio.

The germs of existence contained in this spot of earth, with ample food, and ample room to expand in, would fill millions of worlds in the course of a few thousand years.