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On the Nature of Man
Nemesius of Emesa, tr. Wither, 1636
I. Of the sense of sight, and the opinions of Hipparchus, of the Geometricians, of…
Sect. 1
WE finde that this word fight hath a divers signification; for sometime it signifieth the seat of the sight; and some time the power of the sense (it selfe.)
Hipparchus affirmes that the beams being shot forth from the eyes, take hold (as it were) of outward things with the farthest ends of them (even as if a man should lay his hand on them) and presents (or yeelds) those things, whereof they have so taken hold, to our sight.
But the Geometricians describe unto us Figures (which are called Cones) broad at the first and growing to a narrow top, made by the meeting of the eye-beames in one point. And they hold opinion that the beames of the right-eye, being darted forth to the left-side, and the beames of the left-eye toward the right-side, the Figure CONOS is made by the uniting of them in one; and that thereby it comes to passe that the sight comprehends many visible things together, at one view; and then more exactly perceives them, when the beames are met closely one with another.
And this is the cause, that oftentimes, when we looke upon the pavement we see not a piece of money lying plainly visible thereupon, though wee settle our eyes upon the same with diligence: For, untill it so fall out, that the beames meet in that very place, where the money lyeth, wee still overlooke the same; but then, wee presently attaine the sight of it, as if that had beene the beginning of our looking for it in that place.
The Epicures think that the shapes of such things as appeare unto us, are brought to our eyes.
Aristotle is of opinion that it is not a bodily shape which appeares, but a certaine quality rather conveyed from things visible, unto the sight, by an alteration of the aire which is round about.
IIPlato sayes, that the sight is caused by the meeting of all the severall brightnesses together (that is to say) partly by the light of the eyes, which flowing out some part of the way into the aire, which is of like nature with it selfe; partly by that which is retorted back againe from the bodies which are seene; and partly by the force of that which is extended out together with the fierynesse of the eye, affecting the aire which comes betweene them; and easily spreading every way, or turning to any side.
Galen agreeing with Plato, speaketh of the sight (here and there in some places of his seventh booke of the agreement of parts) much to this purpose If (saith hee) any part or power, or quality of bodies that are visible, should come unto the eye, wee could not know the quantity of the thing seen. For, if a very great mountaine were the object, it were quite contrary to reason, to imagine that the shape of so huge a thing should enter wholly into our eyes: yea, and the spirit belonging to the sight, being darted forth could not bee able to collect together so much vigour, as would bee requisite to comprehend the whole visible object.
It remaines therefore that the aire, wherewith we are encompassed, is after a sort such an instrument unto us when we see, as the nerve which belongeth unto the sight is to the body; and some such thing seemeth to happen to the aire, which encloseth us round: For, the bright shining Sun having touched the upper limits of the aire, distributes his power into the whole aire: And the splendor which is caried through the sinewes called the optick nerves which belong unto the sight, hath his essence of the nature of the spirits: This falling into the aire which is dilated round about us, makes an alteration even at the very first injection, and shootes forth very farre: yet so, that it containes it self undispersed, untill it happen upon a reflecting body.
For, the aire is such an instrument unto the eye, to discerne visible objects, as the sinew is unto the braine: and look in what case the braine is, in respect of his sinew; in like case is the eye in respect of the aire, after it is quickned by the bright shining of the Sun.
Now, that it is the nature of the aire, to become like unto those things which enter into it, appeares manifest by this, that whensoever any bright thing, (be it red or blew, or of the colour of silver) shall bee conveyed through the aire, when it is light, the colour of the aire will bee changed according to that thing which is caried through the same.
But, Porphyrie in his book IIIwhich hee wrote of the senses, affirms, that neither the making of the Figure Conos, neither any shape, nor any other thing, is cause of our seeing, but only this; that the soul her selfe meeting with such objects as are visible, doth perceive and know, that all those things which are seene, be contained in her selfe; because it is she only which holds them together, to their preservation. For, (as he saith) whatsoever is in the world, is nothing else, but the soul holding together divers bodies.
And it were not untruly said, that the soul commeth to the knowledge of it selfe, by the view of every thing which is in the world; if his opinion be allowed: for according to his tenet, there is but one soul for all things, even the reasonable-soul.
Sect. 2
I. Of the proper object of sight, and of such other meanes and circumstances as are usefull in seeing. II. Though colour and shape are onely the proper objects of sight; yet by cogitation and memory, it commeth to the knowledge of other qualities in the thing seene. III. Of such senses as are conversant about things at a distance; and in what cases the sight erres, or needs the aide of other senses.
The sight seeth by straight lines; but it feeleth first & principally the colours of things; and together with thē, discerneth also the body that is coloured, the magnitude, the shape, the place, wherein it is; the distance, the number, the motion, and the rest thereof; as like wise, whether it be rough, or smooth, or unequall, or even, or sharpe, or dull, or what element is predominant therin; and whether it be waterish, or earthy; moist or dry.
Yet that which is the proper object of this sense, is colour onely; for wee no way attaine the knowledge of colours but by our sight: and assoone as wee behold the colour, wee therewithall do immediately perceive also the coloured body; the place wherein the visible object abideth; and the distance, which is between the se〈•〉r and the thing seene.
Looke in how many senses wee receive the knowledge of b〈•〉dily things; even in so many wee come to the knowledge of a place, together with the body; as it is in touching, and tasting: but these two, feele them onely when they are joyned neare unto the body (except in those things which we shall speake of anon) whereas the sight, beholds things at a great distance.
Now in that the sight IIlaies hold of such things, as are visible, when they be far off, it must necessarily follow that it receives a sight only of the distance of things: and it is then only capable of the magnitude of things, when it is able at one view to comprehend the thing which appeareth; but whensoever the visible body is too large to bee apprehended at one aspect, then the sight needeth memory and cogitation to assist it.
For, the sight beholding so great an object by peece-meale (and not at one whole view) must necessarily passe from one part thereof to another; and in that passage, so much onely is apprehended by the proper faculty of the sight, as is present in view; the rest which was viewed before, is kept by the memory, untill our understanding hath brought together, both that which was before seen and that which is present likewise, in our sight.
Moreover, sight apprehends the magnitude of bodies two maner of wayes; Sometime by it selfe alone; and sometime again by the aide of memory and cogitation: But by it selfe alone, it never taketh notice of the number of things visible if they exceed three or foure; seeing the number of them cannot not be discerned at one attempt; neither can it lay hold on the motions of things; neither on Figures which have many corners, without it have the helpe of memory and cogitation to assist it.
For sight is not able to bring together, five or sixe or seaven, or more, without the helpe of memory; neither can it bring together figures that have six, eight, or many corners. The motion also that commeth by passing from one great thing, to another, hath in the same, some what preceding, and somewhat following after; and wheresoever things are found to bee some first, some second, and some third; there memory onely is the preserver of them together: But these qualities, high and low, equall and unequall, rough and smooth, sharpe and dull, bee communicable both to the touching, and to the sight; for that they onely can discerne of place; and yet they stand in some need also of our understanding.
For, that thing onely which moves the sense by one only attempt, is wrought by the sense alone (without the helpe of memory and cogitation:) but, such things as are felt at divers times are not wrought by the sense onely, but by the aide of memory and cogitation, as is aforesaid.
Such is the nature of sight, that it can pierce even unto the bottome of transparant things; and first, and specially of the Aire: For it can passe quite through it. Secondly, it can passe through water when it is cleare; insomuch that wee may see fishes swimming in the same: And; (though somwhat more hardly) it passes through earth, being of a glassie or such like transparant nature. Yet, this is alwayes to be supposed, that these things must be enlightned, when they become the proper object of sight, without the aide of any other assistant.
But let no man bee so deceived, as to imagine that the sight may of it selfe discerne hot things; because when wee see fire, we know that it is hot; for if you refer that speech to the first function of sight, you shall finde that when the sight first beheld the fire, it perceived nothing but the shape and colour thereof. After that, wee comming to touch it, and thereby knowing the same to be hot, our memory preserves in us the knowledge which wee first gained by the touch: and ever since; when wee behold fire (though wee see nothing in it but the shape and colour) our understanding by the helpe of memory, conceives the hear of the fire to be in the same, as well as the things which are properly seene.
The like may be said of an apple; For seeing the whole forme thereof consisteth not onely in the colour and the shape, but in the smell also and in the tast; it followes not that it is the sight onely, whereby we know the same to bee an apple (because we saw the shape and colour of it) for, our memory had preserved in our understanding the experience which we had formerly collected from the smell and tast; and these being added unto that, whereof the eye tooke notice, perfited our knowledge.
Therefore, when wee thinke an apple made of waxe to be a true apple, it is our understanding which erreth, and not our sight; for the sight failed not to informe rightly, so much as pertained unto her sense; when it perceived the true colour and shape of an apple.
Now, these three senses, IIIsight, hearing, and smelling, are conversant about things at a distance, and such as are not joyned close unto them by means of the aire comming between them. But the tast cannot possibly feele any thing but that whereunto it is nearely joyned; and the touching taketh part of both: for sometime wee touch things bodily, without any intermedium betweene us and them; somtime againe, wee touch them with a staffe betwixt us, and the things touched.
Moreover, the sight hath now and then, want of some other of the senses to witnesse unto it the certainty of that which it perceiveth, when things are artificially wrought to deceive the sight; as it falleth out in painting: For, it is the painters cunning to deceive the eye, with counterfeit shadowings, either of an Embost or hollowworke, as the nature of the things requires: To the discerning whereof, the sense of touching is especially usefull, and sometime of the tast and smell also; as appeared in the example of the apple made of wax. Yea, and otherwhile (at no great distance) the sight it selfe maketh some things appeare unto us to bee that which they are not: For, if a towne which is foure-square bee but a pretty distance from us, it will seeme unto the sight to be round.
The sight erres likewise, when wee looke through a thick aire, or through smoake, or some such things as otherwise trouble the sight by the thicknesse thereof. In like maner, when we see things in the water, being stirred; for in the Sea an Oare seemeth broken when it is whole.
So is it also when wee looke in or through some transparant bodie; as looking-glasses, or other glasses and the like things; or when the visible object is moved swiftly: For, a swift-motion so distempers the sight; that those things are thereby made appeare to be round which are nothing so, and those to bee fixed, which are moved.
The same happeneth, when the minde is busied about other matters; as when a man (purposing to meet his friend) passeth by without heeding him whom hee went to meet, (though hee met him in the way) by reason he had his minde busied with other thoughts: But, indeed this is not properly an error of the sight, but of the minde: For, the sight beheld his friend, and gave warning; but the minde heeded not that which was brought unto it.
Finally, the sight needeth foure things for the cleare discerning of all visible objects, namely; A whole and sound seat for that sense; a proportionable measure of motion; a fit distance; and the aire to bee pure and cleare.