Necessity is the mistress and guide of nature.

The painter will produce pictures of little merit if he takes the works of others as his standard.

The wisest and noblest teacher is nature itself.

Supreme happiness will be the greatest cause of misery, and the perfection of wisdom the occassion of folly.

A deaf and dumb person who sees two men in conversation - may nevertheless understand from the attitudes and gestures of the speakers, how well their discussion is getting along.

To speak of this subject you must... explain the nature of the resistance of the air, in the second the anatomy of the bird and its wings, in the third the method of working the wings in their various movements, in the fourth the power of the wings and the tail when the wings are not being moved and when the wind is favourable to serve as guide in various movements.

Wisdom is the daughter of experience