The vices and moral weakness of man are not invincible: Man is perfectible, or in other words, susceptible of perpetual improvement.

as long as a
great number of those impressions which form character, like the nice
motions of the arm, remain absolutely independent of the will of man,
though it would be the height of folly and presumption to attempt to
calculate the relative proportions of virtue and vice at the future periods
of the world, it may be safely asserted that the vices and moral
weakness of mankind, taken in the mass, are invincible.

The power of population is indefinitely greater than the power in the earth to produce subsistence for man.

The main peculiarity which distinguishes man from other animals is the means of his support-the power which he possesses of very greatly increasing these means.

A writer may tell me that he thinks man will ultimately become an ostrich. I cannot properly contradict him.

Morality is the weakness of the brain.