The ordeal of virtue is to resist all temptation to evil.

The greatest talents have been frequently misapplied and have produced evil proportionate to the extent of their powers. Both reason and revelation seem to assure us that such minds will be condemned to eternal death, but while on earth, these vicious instruments performed their part in the great mass of impressions, by the disgust and abhorrence which they excited.

The natural inequality of the two powers of population and of production in the earth, and that great law of our nature which must constantly keep their efforts equal, form the great difficulty that to me appears insurmountable in the way to the perfectibility of society.

In a state therefore of great equality and virtue, where pure and simple manners prevailed, the increase of the human species would evidently be much greater than any increase that has been hitherto known.

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

I do not know that any writer has supposed that on this earth man will ultimately be able to live without food.

The moon is not kept in her orbit round the earth, nor the earth in her orbit round the sun, by a force that varies merely in the inverse ratio of the squares of the distances.