Nothing will be left, Nothing in the air, nothing under the earth, nothing in the waters. All will be exterminated.

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

I have always felt it is my destiny to build a machine that would allow man to fly.

Ask counsel of him who rules himself well.

I think it is no small attraction in a painter to be able to give a pleasing air to his figures, and whoever is not naturally possessed of this grace may acquire it by study, as opportunity offers in the following manner: be on the watch to take good parts of many beautiful faces of which the beautiful parts are established by general repute rather than by your own judgement, for you may deceive yourself by selecting faces that resemble your own, since it often seems that such similarities please us; ... so therefore choose the beautiful ones as I tell you and fix them in your mind.

Nature never breaks her own laws.

The earth is moved from its position by the weight of a tiny bird resting upon it.