Art is the queen of all sciences communicating knowledge to all the generations of the world. - Leonardo da Vinci

Anyone who in discussion quotes authority uses his memory rather than his intellect.

Represent your figures in such action as may be fitted to express what purpose is in the mind of each; otherwise your art will not be admirable.

If you take as your pattern the wings of feathered birds, these are more powerful in structure of bone and sinew because they are penetrable, that is to say the feathers are separated from one another and the air passes through them. But the bat is aided by its membrane, which binds the whole together and is not penetrated by the air.