Ku K'ai-Chih (Chinese, fourth century A.D.).
XIII
First it is necessary to know what this sort of imitation is, and to define it.
Definition:
It is an imitation made with lines and with colours on some plane surface of everything that can be seen under the sun. Its object is to give delight.
Principles which may be learnt by all men of reason:
No visible object can be presented without light.
No visible object can be presented without a transparent medium.