Department of History
Week 2. Transmission Trouble
On the Nature of Things (c. 1190)
It is generally conceded that the more remote a thing, the smaller it appears. However, vapor can and commonly does prevent this general occurrence, for the body of the sun appears larger toward dawn on account of the remains of the nocturnal vapors than when it shines at midday. Moreover, a fish or anything placed in water seems larger in the water than out of it. Thus a dog swimming in water holding a piece of meat in its mouth is deceived by seeing a shadow and lets go of the meat that it was holding in its mouth, hoping to secure a larger piece for itself, but in vain. Let the waters represent tribulations; martyrs placed in tribulations were greater than in time of peace. The sun stands for power, which seems greater the more remote it is. Something worthy of admiration is found also in geometrical investigations: there is something that appears larger the more remote it is; for the closer the angle of tangency, the smaller it appears to be.... Similarly, the further the acquaintance of a powerful man is from being achieved, the more worthy of praise is he considered to be. [However,] having become the friend of the powerful man, so much less desirable will his friendship appear to you....
Likewise, a straight rod appears bent in water, which is customarily attributed to reflection of the rays from the surface of the water. [Now,] waters represent tribulations and the straight rod good works. Thus the works of the just, who are vexed by tribulations, are often regarded as bent, although they are [actually] straight. Furthermore, the man who is in a dark place sees a man standing in the light, but not vice versa; in the same way, unimportant people, whose fortune is dark, perceive the deeds of important people, but not vice versa.
A marvelous thing can be observed [even] by somebody poorly instructed in such things, since no parallel lines appear to be parallel.
A denarius placed in the bottom of a basin filled with water will be seen by one standing far away; when the water is drawn off, it will not be seen. Likewise, as long as there is tribulation in the soul, many things are observed and perceived which are not perceived when the tribulation has been removed. And as too much prosperity blinds the mind, so tribulation restores keener sight to the mind. Some one wishing to maintain that the denarius is not seen will contend that the water itself represents such a form to the eyes of the observer. To another, it will seem that a shadow appears because of the reflection made in the lucid body. But I think Aristotle is more to be believed than the masses.
To a person looking into water a tower not far removed from the water will appear to be inverted, although it is actually straight and erect; rejoice in the vanities of things, and they who do well will seem to you not to be standing upright, but inverted. An image is not formed in turbulent water but in quiet water; so also a disturbed mind is not attentive; anger hinders the soul, so that it cannot discern truth.
Although the body of the sun is round, it does not appear to have a convex surface, which occurs because of the impotence of sight and the excessive splendor of the sun. Similarly, the status of important men does not appear as it really is because of the splendor of the vainglory of conspicuous men; it is subject to the vicissitudes of life, although to the less prudent it appears otherwise. Furthermore, many are lifted in spirit who appear perfectly flat. Is it more necessary to ignore their thoughts than [those of] this powerful man? It is necessary that he fear many, who is feared by many.
Notice how certain animals see at night but not during the day on account of the whiteness of their eyes and the subtlety of their visual spirit. For during the day the visual spirit (inasmuch as it is subtle and bright) is easily dispersed by the brightness of the air striking against the eyes, the whiteness of the eyes cooperating in this separation; and thus the power of sight of the spirits is darkened by perdition. But at night, aided and strengthened by the darkness of the air, the visual spirit illuminates (by its own brightness) the air between the seeing thing and the thing to be seen, and thus it prepares the way for discerning the thing opposite; and this is evident in owls. In other animals, illuminated by the brightness of the day, the visual spirit produces sight during the day, because the eyes [of those animals] are black and the visual spirit is gross and dark; but at night, darkened by much greater obscurity, it does not perfect sight, but confuses it; and this is seen clearly in men. However, in bats, because their instruments [of perception] are varied and their visual spirit is midway between darkness and brightness, sight is achieved only at dawn or at dusk, because of the mediocrity [at those times] of the air; for during the day, because of the excessive brightness dividing the spirit, and at night, because of the excessive darkness obscuring the spirit, vision is as far removed from the bat as activity. So bright and subtle is the visual spirit in a lynx that by its irradiation, illuminating the dark air contained in the pores of a wall, the spirit is moved to see something placed on the other side of the wall. The eagle, however, although it has an excellent organ of vision (both because its visual spirit is strong and because its pupil is small, on which account very little of the spirit is scattered outside), exposes its eyes to the rays of the sun and [yet] directs its eyes without injury to seeing. But in us, because there is not so much visual spirit and the pupil of the eye is large, we are unable to look at the sun for very long on account of the [resulting] excessive dissolution of the spirits.
The basilisk [a fabulous lizard] is said to kill man by sight alone, for it infects the air with the badness of its ray. The visual ray of a wolf is productive of stupor, and a man appearing unexpectedly and seen by a wolf is struck dumb for a time. Wherefore they say that bewitching is produced by the badness of the ray of the seeing thing; and this is why nurses lick the face of a bewitched little boy.
But if a ray issues forth, it is marvelous how it perceives the surface of the solar body, for the sun is 166 times and a fraction larger than the whole earth. This is why it appears to very inquisitive men that the sun is not [really] seen but that air adjacent to the earth and subject to the sun is seen. For how is the ray issuing forth turned back? How also can the ray be emitted [both] yesterday and today, or is a new ray emitted by the eye at every single instant? Moreover, when a certain man is sitting in a different place from others, how do those men see him if the rays emitted from their eyes [that is, his as well as theirs] encounter one another? Also, will one of the rays withdraw from the other, or will there be two rays [in the same place] at the same time? Also, since the stars are much more distant from us than is the sun, how does a small ray extend itself to such a remote place without becoming thinner as it approaches the more remote obstacle? However, to him who is well instructed in physics, it is not doubtful that the visual ray is sent from the lining of the brain through the optic nerve to the window of the eye. And note how the two rays sent to the eyes intersect each other transversely in the form of a cross; just as without faith in the cross the inner man does not see well, so neither is exterior vision achieved without the form of the cross. It should be noted also that a gross vapor sometimes unites itself to a visual ray, whence certain small black bodies sometimes appear to flit before human eyes....
Concerning the mirror.
When a mirror is whole, there being but one observer, only one image is produced; but should the glass be broken into several pieces, there appear as many images as there are breaks. And thus in Holy Scripture, as many understandings shine forth as there are expositions. But, marvelous thing!, remove the lead placed behind the glass; immediately no image is visible to the observer. [Likewise,] remove the foundation of the faith, and immediately you will no longer see yourself clearly in Holy Scripture. The lead can be understood to represent sin; thus in the mirror of Holy Scripture you will discern yourself less clearly unless you confess yourself to be a sinner. For if we say that we have not sinned, we deceive ourselves, and the truth is not in us.
In a concave mirror, the image of the observer appears inverted; in a plane and convex mirror, erect. Who will provide a sufficient explanation of this?
Also the pupil, which is a very small substance, is a mirror, in which the image of the observer shines back. However, for three days before the death of a man, the brightness of the pupil is already darkened, so that for [those] three days the image of an observer does not appear in it.
The image appearing in a mirror appears to conform itself to that of which it is the image. It laughs at a laughing person, and when the observer cries, the image seems to cry [also]. Thus the soul is the mirror of its Maker and ought to sympathize with the suffering Christ and rejoice with the risen and rejoicing Christ. Therefore, at different times different countenances are to be assumed, so long as we always have the countenance of one proceeding toward Jerusalem....