But as to the nature of the sensory4 organs, or parts of the body in which each of the senses is naturally implanted, inquirers now usually take as their guide the fundamental elements of bodies. Not, however, finding it easy to coordinate5 five senses with four elements, they are at a loss respecting the fifth sense. But they hold the organ of sight to consist of fire, being prompted to this view by a certain sensory affection of whose true cause they are ignorant. This is that, when the eye is pressed or moved, fire appears to flash from it. This naturally takes place in darkness, or when the eyelids6 are closed, for then, too, darkness is produced.
This theory, however, solves one question only to raise another; for, unless on the hypothesis that a person who is in his full senses can see an object of vision without being aware of it, the eye must on this theory see itself. But then why does the above affection not occur also when the eye is at rest? The true explanation of this affection, which will contain the answer to our question, and account for the current notion that the eye consists of fire, must be determined7 in the following way: Things which are smooth have the natural property of shining in darkness, without, however, producing light. Now, the part of the eye called ‘the black’, i.e. its central part, is manifestly smooth. The phenomenon of the flash occurs only when the eye is moved, because only then could it possibly occur that the same one object should become as it were two. The rapidity of the movement has the effect of making that which sees and that which is seen seem different from one another. Hence the phenomenon does not occur unless the motion is rapid and takes place in darkness. For it is in the dark that that which is smooth, e.g. the heads of certain fishes, and the sepia of the cuttle-fish, naturally shines, and, when the movement of the eye is slow, it is impossible that that which sees and that which is seen should appear to be simultaneously8 two and one. But, in fact, the eye sees itself in the above phenomenon merely as it does so in ordinary optical reflexion.
If the visual organ proper really were fire, which is the doctrine10 of Empedocles, a doctrine taught also in the Timaeus, and if vision were the result of light issuing from the eye as from a lantern, why should the eye not have had the power of seeing even in the dark? It is totally idle to say, as the Timaeus does, that the visual ray coming forth11 in the darkness is quenched12. What is the meaning of this ‘quenching’ of light? That which, like a fire of coals or an ordinary flame, is hot and dry is, indeed, quenched by the moist or cold; but heat and dryness are evidently not attributes of light. Or if they are attributes of it, but belong to it in a degree so slight as to be imperceptible to us, we should have expected that in the daytime the light of the sun should be quenched when rain falls, and that darkness should prevail in frosty weather. Flame, for example, and ignited bodies are subject to such extinction13, but experience shows that nothing of this sort happens to the sunlight.
Empedocles at times seems to hold that vision is to be explained as above stated by light issuing forth from the eye, e.g. in the following passage:—
As when one who purposes going abroad prepares a lantern,
A gleam of fire blazing through the stormy night,
Adjusting thereto, to screen it from all sorts of winds,
transparent14 sides,
Which scatter15 the breath of the winds as they blow,
While, out through them leaping, the fire,
i.e. all the more subtile part of this,
Shines along his threshold old incessant16 beams:
So [Divine love] embedded17 the round “lens”, [viz.]
the primaeval fire fenced within the membranes18,
In [its own] delicate tissues;
And these fended20 off the deep surrounding flood,
While leaping forth the fire, i.e. all its more subtile part-.
Sometimes he accounts for vision thus, but at other times he explains it by emanations from the visible objects.
Democritus, on the other hand, is right in his opinion that the eye is of water; not, however, when he goes on to explain seeing as mere9 mirroring. The mirroring that takes place in an eye is due to the fact that the eye is smooth, and it really has its seat not in the eye which is seen, but in that which sees. For the case is merely one of reflexion. But it would seem that even in his time there was no scientific knowledge of the general subject of the formation of images and the phenomena21 of reflexion. It is strange too, that it never occurred to him to ask why, if his theory be true, the eye alone sees, while none of the other things in which images are reflected do so.
True, then, the visual organ proper is composed of water, yet vision appertains to it not because it is so composed, but because it is translucent22 — a property common alike to water and to air. But water is more easily confined and more easily condensed than air; wherefore it is that the pupil, i.e. the eye proper, consists of water. That it does so is proved by facts of actual experience. The substance which flows from eyes when decomposing23 is seen to be water, and this in undeveloped embryos24 is remarkably25 cold and glistening26. In sanguineous animals the white of the eye is fat and oily, in order that the moisture of the eye may be proof against freezing. Wherefore the eye is of all parts of the body the least sensitive to cold: no one ever feels cold in the part sheltered by the eyelids. The eyes of bloodless animals are covered with a hard scale which gives them similar protection.
It is, to state the matter generally, an irrational27 notion that the eye should see in virtue28 of something issuing from it; that the visual ray should extend itself all the way to the stars, or else go out merely to a certain point, and there coalesce29, as some say, with rays which proceed from the object. It would be better to suppose this coalescence30 to take place in the fundament of the eye itself. But even this would be mere trifling31. For what is meant by the ‘coalescence’ of light with light? Or how is it possible? Coalescence does not occur between any two things taken at random32. And how could the light within the eye coalesce with that outside it? For the environing membrane19 comes between them.
That without light vision is impossible has been stated elsewhere; but, whether the medium between the eye and its objects is air or light, vision is caused by a process through this medium.
Accordingly, that the inner part of the eye consists of water is easily intelligible33, water being translucent.
Now, as vision outwardly is impossible without [extra-organic] light, so also it is impossible inwardly [without light within the organ]. There must, therefore, be some translucent medium within the eye, and, as this is not air, it must be water. The soul or its perceptive34 part is not situated35 at the external surface of the eye, but obviously somewhere within: whence the necessity of the interior of the eye being translucent, i.e. capable of admitting light. And that it is so is plain from actual occurrences. It is matter of experience that soldiers wounded in battle by a sword slash36 on the temple, so inflicted37 as to sever38 the passages of [i.e. inward from] the eye, feel a sudden onset39 of darkness, as if a lamp had gone out; because what is called the pupil, i.e. the translucent, which is a sort of inner lamp, is then cut off [from its connexion with the soul].
Hence, if the facts be at all as here stated, it is clear that — if one should explain the nature of the sensory organs in this way, i.e. by correlating each of them with one of the four elements — we must conceive that the part of the eye immediately concerned in vision consists of water, that the part immediately concerned in the perception of sound consists of air, and that the sense of smell consists of fire. (I say the sense of smell, not the organ.) For the organ of smell is only potentially that which the sense of smell, as realized, is actually; since the object of sense is what causes the actualization of each sense, so that it (the sense) must (at the instant of actualization) be (actually) that which before (the moment of actualization) it was potentially. Now, odour is a smoke-like evaporation40, and smoke-like evaporation arises from fire. This also helps us to understand why the olfactory41 organ has its proper seat in the environment of the brain, for cold matter is potentially hot. In the same way must the genesis of the eye be explained. Its structure is an offshoot from the brain, because the latter is the moistest and coldest of all the bodily parts.
The organ of touch proper consists of earth, and the faculty42 of taste is a particular form of touch. This explains why the sensory organ of both touch and taste is closely related to the heart. For the heart as being the hottest of all the bodily parts, is the counterpoise of the brain.
This then is the way in which the characteristics of the bodily organs of sense must be determined.
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1
distinctive
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| adj.特别的，有特色的，与众不同的 | |
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potency
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| n. 效力，潜能 | |
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faculties
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| n.能力( faculty的名词复数 )；全体教职员；技巧；院 | |
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4
sensory
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| adj.知觉的，感觉的，知觉器官的 | |
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coordinate
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| adj.同等的，协调的；n.同等者；vt.协作，协调 | |
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6
eyelids
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| n.眼睑( eyelid的名词复数 )；眼睛也不眨一下；不露声色；面不改色 | |
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determined
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| adj.坚定的；有决心的 | |
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simultaneously
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| adv.同时发生地，同时进行地 | |
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9
mere
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| adj.纯粹的；仅仅，只不过 | |
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10
doctrine
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| n.教义；主义；学说 | |
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11
forth
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| adv.向前；向外，往外 | |
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12
quenched
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| 解（渴）( quench的过去式和过去分词 )； 终止（某事物）； （用水）扑灭（火焰等）； 将（热物体）放入水中急速冷却 | |
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13
extinction
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| n.熄灭，消亡，消灭，灭绝，绝种 | |
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14
transparent
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| adj.明显的，无疑的；透明的 | |
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15
scatter
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| vt.撒，驱散，散开；散布/播；vi.分散，消散 | |
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16
incessant
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| adj.不停的，连续的 | |
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embedded
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| a.扎牢的 | |
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18
membranes
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| n.（动物或植物体内的）薄膜( membrane的名词复数 )；隔膜；（可起防水、防风等作用的）膜状物 | |
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19
membrane
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| n.薄膜，膜皮，羊皮纸 | |
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20
fended
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| v.独立生活，照料自己( fend的过去式和过去分词 )；挡开，避开 | |
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21
phenomena
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| n.现象 | |
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22
translucent
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| adj.半透明的；透明的 | |
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23
decomposing
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| 腐烂( decompose的现在分词 )； （使）分解； 分解（某物质、光线等） | |
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24
embryos
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| n.晶胚；胚，胚胎( embryo的名词复数 ) | |
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25
remarkably
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| ad.不同寻常地，相当地 | |
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26
glistening
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| adj.闪耀的，反光的v.湿物闪耀，闪亮( glisten的现在分词 ) | |
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27
irrational
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| adj.无理性的，失去理性的 | |
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28
virtue
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| n.德行，美德；贞操；优点；功效，效力 | |
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29
coalesce
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| v.联合，结合，合并 | |
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30
coalescence
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| n.合并，联合 | |
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31
trifling
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| adj.微不足道的；没什么价值的 | |
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32
random
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| adj.随机的；任意的；n.偶然的(或随便的)行动 | |
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33
intelligible
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| adj.可理解的，明白易懂的，清楚的 | |
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34
perceptive
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| adj.知觉的，有洞察力的，感知的 | |
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35
situated
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| adj.坐落在...的，处于某种境地的 | |
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36
slash
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| vi.大幅度削减；vt.猛砍，尖锐抨击，大幅减少；n.猛砍，斜线，长切口，衣衩 | |
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37
inflicted
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| 把…强加给，使承受，遭受( inflict的过去式和过去分词 ) | |
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38
sever
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| v.切开，割开；断绝，中断 | |
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39
onset
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| n.进攻，袭击，开始，突然开始 | |
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40
evaporation
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| n.蒸发，消失 | |
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41
olfactory
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| adj.嗅觉的 | |
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42
faculty
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| n.才能；学院，系；(学院或系的)全体教学人员 | |
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