Plato, Timaeus

[68a] and dissolving the very passages of the eyes causes a volume of fire and water to pour from them, which we call “tears.” And this moving body, being itself fire, meets fire from the opposite direction; and as the one firestream is leaping out like a flash, and the other passing in and being quenched in the moisture, in the resultant mixture colors of all kinds are produced. This sensation we term “dazzling” and the object which causes it “bright” or “brilliant.” Again, when the kind of fire [68b] which is midway between these¹ reaches to the liquid of the eyes and is mingled therewith, it is not brilliant but, owing to the blending of the fire's ray through the moisture, it gives off a sanguine color, and we give it the name of “red.” And “bright” color when blended with red and white becomes “yellow.” But in what proportions the colors are blended it were foolish to declare, even if one knew, seeing that in such matters one could not properly adduce any necessary ground or probable reason. Red blended with black and white makes “purple”; [68c] but when these colors are mixed and more completely burned, and black is blended therewith, the result is “violet.” “Chestnut” comes from the blending of yellow and grey; and “grey” from white and black; and “ochre” from white mixed with yellow. And when white is combined with “bright” and is steeped in deep black it turns into a “dark blue” color; and dark blue mixed with white becomes “light blue”; and chestnut with black becomes “green.” As to the rest, it is fairly clear from these examples [68d] what are the mixtures with which we ought to identify them if we would preserve probability in our account. But should any inquirer make an experimental test of these facts, he would evince his ignorance of the difference between man's nature and Gods—how that, whereas God is sufficiently wise and powerful to blend the many into one and to dissolve again the one into many, there exists not now, nor ever will exist hereafter, a child of man sufficient for either of these tasks. [68e]

Such, then, being the necessary nature of all these things, the Artificer of the most fair and good took them over at that time amongst things generated when He was engendering the self-sufficing and most perfect God; and their inherent properties he used as subservient causes, but Himself designed the Good in all that was being generated. Wherefore one ought to distinguish two kinds of causes,² the necessary and the divine, and in all things to seek after the divine for the sake of gaining a life of blessedness, so far as our nature admits thereof,