Quaestiones Convivales
Plutarch
Plutarch. Plutarch's Morals, Vol. III. Goodwin, William W., editor; Creech, Thomas, translator. Boston: Little, Brown, and Company; Cambridge: Press of John Wilson and Son, 1874.
Some answered, that they did not remove the book to lessen the light, but to receive more rays, and let all the space between the letters and their eyes be filled with
lightsome air. Others agreed with those that imagine the rays of vision mix with one another; for since there is a cone stretched between each eye and the object, whose point is in the eye and whose basis is the object, it is probable that for some way each cone extends apart and by itself; but, when the distance increases, they mix and make but one common light; and therefore every object appears single and not two, though it is seen by both eyes at once; for the conjunction of the cones makes these two appearances but one. These things supposed, when old men hold the letters near to their eyes, the cones not being joined, but each apart and by itself, their sight is weak; but when they remove it farther, the two lights being mingled and increased, they see better, as a man with both hands can hold that for which either singly is too weak.But my brother Lamprias, though unacquainted with Hieronymus’s notions, gave us the same reason. We see, said he, some species that come from the object to the eye, which at their first rise are thick and great, and therefore when near disturb old men, whose eyes are stiff and not easily penetrated; but when they are separated and diffused into the air, the thick obstructing parts are easily removed, and the subtile remainders coming to the eye slide gently and easily into the pores; and so the disturbance being less, the sight is more vigorous and clear. Thus a rose smells most fragrant at a distance; but if you bring it near the nose, it is not so pure and delightful; and the reason is this,—many earthy disturbing particles are carried with the smell, and spoil the fragrancy when near, but in a longer passage those are lost, and the pure brisk odor, by reason of its subtility, reaches and acts upon the sense.
But we, according to Plato’s opinion, assert that a bright spirit darted from the eye mixes with the light
about the object, and those two are perfectly blended into one similar body; now these must be joined in due proportion one to another; for one part ought not wholly to prevail on the other, but both, being proportionally and amicably joined, should agree in one third common power. Now this (whether flux, illuminated spirit, or ray) in old men being very weak, there can be no combination, no mixture with the light about the object; but it must be wholly consumed, unless, by removing the letters from their eyes, they lessen the brightness of the light, so that it comes to the sight not too strong or unmixed, but well proportioned and blended with the other. And this explains that common affection of creatures seeing in the dark; for their eye-sight being weak is overcome and darkened by the splendor of the day; because the little light that flows from their eyes cannot be proportionably mixed with the stronger and more numerous beams; but it is proportionable and sufficient for the feeble splendor of the stars, and so can join with it, and co-operate to move the sense.THEON the grammarian, when Metrius Florus gave us an entertainment, asked Themistocles the Stoic, why Chrysippus, though he frequently mentioned some strange phenomena in nature (as that salt fish soaked in salt water grows fresher than before, fleeces of wool are more easily separated by a gentle than a quick and violent force, and men that are fasting eat slower than those who took a breakfast), yet never gave any reason for the appearance. And Themistocles replied, that Chrysippus only proposed such things by the by, as instances to correct us, who easily and without any reason assent to what seems likely,
and disbelieve every thing that seems unlikely at the first sight. But why, sir, are you concerned at this? For if you are speculative and would enquire into the causes of things, you need not want subjects in your own profession; but pray tell me why Homer makes Nausicaa wash in the river rather than the sea, though it was near, and in all likelihood hotter, clearer, and fitter to wash with than that?