Subsistence increases only in an arithmetical ratio.

No move towards the extinction of the passion between the sexes has taken place in the five or six thousand years that the world has existed.

The great and unlooked for discoveries that have taken place of late years have all concurred to lead many men into the opinion that we were touching on a period big with the most important changes.

It is an acknowledged truth in philosophy that a just theory will always be confirmed by experiment.

The finest minds seem to be formed rather by efforts at original thinking, by endeavours to form new combinations, and to discover new truths, than by passively receiving the impressions of other men's ideas.

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

[P]opulation, when unchecked, goes on doubling itself every twenty-five years, or increases in a geometrical ratio. ... [T]he means of subsistence, under circumstances the most favorable to human industry, could not possibly be made to increase faster than in an arithmetical ratio.