All our knowledge has its origins in our perceptions.

The men of experiment are like the ant; they only collect and use. But the bee...gathers its materials from the flowers of the garden and of the field, but transforms and digests it by a power of its own.

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.

Make your work to be in keeping with your purpose

Great love is born of great knowledge of the thing that is loved, and if you do not know it, you can love it little or not at all.

Avoid the precepts of those thinkers whose reasoning is not confirmed by experience.

Nothing is so much to be feared as Evil Report.