"The mind of the painter should be like a mirror which always takes the colour of the thing that it reflects and which is filled by as many images as there are things placed before it. ...And do not after the manner of some painters who when tired by imaginative work, lay aside their task... keeping... such weariness of mind as prevents them either seeing or being conscious of different objects; so that often when meeting friends or relatives, and being saluted by them, although they may see and hear them they know them no more than if they had met only so much air."