All our knowledge has its origins in our perceptions.

Where the spirit does not work with the hand, there is no art.

Nature is constrained by the cause of her laws which dwell inborn in her. Variant: Nature is constrained by the order of her own law which lives and works within her.

For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.

Learning is the only thing that never disappoints us.

Threats alone, are the weapons of the threatened man.

We, by our arts may be called the grandsons of God.