Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory.

But you who live on dreams, you are better pleased with the sophistical reasoning and frauds of talkers about great and uncertain matters than those who speak of certain and natural matters, not of such lofty nature.

He who does not punish evil commands it to be done.

He who truly knows has no occasion to shout.

Human subtlety will never devise an invention more beautiful, more simple or more direct than does Nature, because in her inventions, nothing is lacking and nothing is superfluous.

Iron rusts from disuse, stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigors of the mind.

It is easier to resist at the beginning than at the end.

Men of lofty genius are most active when they are doing the least work.

Painting is poetry that is seen rather than felt, and poetry is painting that is felt rather than seen.

The greatest deception men suffer is from their own opinions.

The time will come when men such as I will look upon the murder of animals as they now look on the murder of men.

Truly man is the king of beasts, for his brutality exceeds them. We live by the death of others. We are burial places! I have since an early age abjured the use of meat...

When once you have tasted flight, you will forever walk the Earth with your eyes turned skyward, for there you have been, and there you will always long to return.

Where there is shouting there is no true knowledge.

You can have no dominion greater or less than that over yourself.