The Elements of Law Natural and Politic [2]
and this alone is sufficient for this conclusion: that colour and image may be there where the thing seen is not. But because it may be said that notwithstanding the image in the water be not in the object, but a thing merely phantastical, yet there may be colour really in the thing itself; I will urge further this experience: that divers times men see directly the same object double, as two candles for one, which may happen by distemper, or otherwise without distemper if a man will, the organs being either in their right temper, or equally distempered. The colours and figures in two such images of the same thing cannot be inherent both therein, because the thing seen cannot be in two places: one of these images thereof is not inherent in the object. But seeing the organs of sight are then in equal temper or equal distemper, the one of them is no more inherent than the other, and consequently neither of them both are in the object; which is the first proposition mentioned in the precedent section. 6. Secondly, that the image of any thing seen by reJection in glass or water or the like, is not any thing in or behind the glass, or in or under the water, every man may prove to himself; which is the second proposition. 7. For the third, we are to consider first, that upon every great agitation or concussion of the brain, as it happeneth from a stroke, especially if the stroke be upon the eye, whereby the optic nerve suffereth any great violence, there appeareth before the eyes a certain light, which light is nothing without, but an apparition only, all that is real being the concussion or motion of the parts of that nerve. From which experience we may conclude, that apparition of light without, is really nothing but motion within. If therefore from lucid bodies there can be derived motion, so as to affect the optic nerve in such manner as is proper thereunto, there will follow an image of light somewhere in that line by which the motion was last derived unto the eye; that is to say, in the object, if we look directly on it, and in the glass or water, when we look upon it in the line of reJection, which in effect is the third proposition, namely, That image and colour is but an apparition unto us of that motion, agitation, or alteration, which the object worketh in the brain, or spirits, or some internal substance in the head. 8. But that from all lucid, shining and illuminated bodies, there is a motion produced to the eye, and, through the eye, to the optic nerve, and so into the brain, by which that apparition of light or colour is effected, is not hard to prove. And first, it is evident that the fire, the only lucid body here on earth, worketh by motion equally every way; insomuch as the motion thereof stopped or inclosed, it is presently extinguished, and no more fire. And farther, that that motion, whereby the fire worketh, is dilatation, and contraction of itself alternately, commonly called scintillation or glowing, is manifest also by experience. From such motion in the fire must needs arise a rejection or casting from itself of that part of the medium which is contiguous to it, whereby that part also rejecteth the next, and so successively one part beateth back the other to the very eye; and in the same manner the exterior part of the eye (the laws of refraction still observed) presseth the interior. Now the interior coat of the eye is nothing else but a piece of the optic nerve, and therefore the motion is still continued thereby into the brain, and by resistance or reaction of the brain, is also a rebound in the optic nerve again, which we not conceiving as motion or rebound from within, think it is without, and call it light; as hath been already shewed by the experience of a stroke. We have no reason to doubt, that the fountain of light, the sun, worketh any other wise than the fire, at least in this matter, and thus all vision hath its original from such motion as is here described. For where there is no light, there is no sight; and therefore colour also must be the same thing with light, as being the