(23) First there is the astringent quality, then the sweet, and next the bitter: The sweet is in the midst between the astringent and the bitter. Now the astringent causes things to be hard, cold and dark; and the bitter teareth, driveth, rageth and divideth or distinguished. These two qualities rub and drive each other so hard, and move so eagerly, that they generate the heat, which now in these two qualities is dark, even as heat in a stone is.

(58) And the bitter quality penetrateth into the body, into the astringent or sour and into the sweet qualities, and frameth all sorts of colours according to that quality to which the body is most eagerly inclined, or according to that quality which is strongest in the body, according to that [strongest quality] the bitter quality frameth the body, with its colours, and according to that [same] quality the creature has its greatest impulse and inclination, motion, boiling and will. IV. Of the Fourth Circumstance or Species.

(37) In Meno, Plato, speaking through Socrates, describes color as "an effluence of form, commensurate with sight, and sensible." In Theætetus he discourses more at length on the subject thus: "Let us carry out the principle which has just been affirmed, that nothing is self-existent, and then we shall see that every color, white, black, and every other color, arises out of the eye meeting the appropriate motion, and that what we term the substance of each color is neither the active nor the passive element, but something which passes between them, and is peculiar to each percipient; are you certain that the several colors appear to every animal--say a dog--as they appear to you?"

(71) There the bitter quality penetrateth in the heat through the astringent, and the sweet in the water letteth it easily or gently through; and there the bitter in the heat goeth through the sweet water forth from the body and makes two open gates, which are the eyes, the first sense or sensibility.