Philosophical Letters: or, modest Reflections upon some Opinions in Natural Philosophy. Duchess of Margaret Cavendish Newcastle
But there is some difference between those figures that perceive light, and those that are light themselves; for when we sleep, there is made the figure of light, but not from a copy; but when the eye seeth light, that figure is made from a copy of the real figure of the Sun; but those lights which are inherent, as in Glow-worms-tails, are original lights, in which is as much difference as between a Man and his Picture; and as for the swiftness of the Motions of light, and the violence of the Motions of fire, it is very probable they are so, but they are a certain particular kind or sort of swift and violent motions; neither will all sorts of swift and violent motions make fire or light, as for example the swift and violent Circular motion of a Whirlewind neither makes light nor fire; Neither is all fire light, nor all light fire, for there is a sort of dead fire, as in Spices, Spirits, Oyles, and the like; and several sorts of lights, which are not hot, as the light which is made in Dreams, as also the inherent lights in Glow-worms, Cats-eyes, Fish-bones, and the like; all which several fires and lights are made by the self-moving matter and motions distinguishable by their figures, for those Motions make such a figure for the Suns light, such a figure for Glow-worms light, such a figure for Cats-eyes light, and so some alteration in every sort of light; The same for Fire, onely Fire-light is a mixt figure, as partly of the figure of Fire, and partly of the figure of Light: Also Colours are made after the like manner, viz. so many several Colours, so many several Figures; and as these Figures are less or more different, so are the Colours.
Thus, Madam, whosoever will study Nature, must consider the Figures of every Creature, as well as their Motions, and must not make abstractions of Motion and Figure from Matter, nor of Matter from Motion and Figure, for they are inseparable, as being but one thing, viz. Corporeal Figurative Motions; and whosoever conceives any of them as abstract, will, in my opinion, very much erre; but men are apt to make more difficulties and enforcements in nature then nature ever knew. But to return to Light: There is no better argument to prove that all objects of sight are figured in the Eye, by the sensitive, voluntary or self-motions, without the pressure of objects, but that not onely the pressure of light would hurt the tender Eye, but that the eye doth not see all objects according to their Magnitude, but sometimes bigger, sometimes less: as for example, when the eye looks through a small passage, as a Perspective-glass, by reason of the difficulty of seeing a body through a small hole, and the double figure of the glass being convex and concave, the corporeal motions use more force, by which the object is enlarged, like as a spark of fire by force is dilated into a great fire, and a drop of water by blowing into a bubble; so the corporeal motions do double and treble their strength, making the Image of the object exceeding large in the eye; for though the eye be contracted, yet the Image in the eye is enlarged to a great extension; for the sensitive and rational matter is extremely subtil, by reason it is extreamly pure, by which it hath more means and ways of magnifying then the Perspective-glass. But I intend to write more of this subject in my next, and so I break off here, resting,
Madam,
Your Faithful Friend
and Servant.
[1] Ch. 27.
XX.
MADAM,
Some perhaps will question the truth or probability of my saying, that Light is a Body, objecting that if light were a body, when the Sun is absent or retires under our Horizon, its light would leave an empty place, or if there were no empty place but all full, the light of the Sun at its return would not have room to display it self, especially in so great a compass as it doth, for two bodies cannot be in one place at one time. I answer, all bodies carry their places along with them, for body and place go together and are inseparable, and when the light of the Sun is gone, darkness succeeds, and when darkness is gone, light succeeds, so that it is with light and darkness as with all Creatures else; For you cannot believe, that if the whole World were removed, there would be a place of the world left, for there cannot be an empty nothing, no more then there can be an empty something; but if the world were annihilated, the place would be annihilated too, place and body being one and the same thing; and therefore in my opinion, there be no more places then there are bodies, nor no more bodies then there are places.
Secondly, They will think it absurd that I say, the eye can see without light; but in my opinion it seems not absurd, but very rational, for we may see in dreams, and some do see in the dark, not in their fancy or imagination, but really; and as for dreams, the sensitive corporeal motions make a light on the inside of the organ of sight really, as I have declared in my former Letter. But that we do not see ordinarily without exterior Light, the reason is, that the sensitive Motions cannot find the outward objects to pattern out without exterior light, but all perception doth not proceed from light, for all other perception besides animal sight requires not light. Neither in my opinion, doth the Perception of sight in all Creatures but Animals, but yet Animals do often see in the dark, and in sleep: I will not say but that the animate matter which by self-motion doth make the Perception of light with other perceptive Figures, and so animal perceptive light may be the presenter or ground perceptive figure of sight; yet the sensitive corporeal motions can make other figures without the help of light, and such as light did never present: But when the eye patterns out an exterior object presented by light, it patterns also out the object of light; for the sensitive motions can make many figures by one act, not onely in several organs, but in one organ; as for example, there is presented to sight a piece of Imbroydery, wherein is silk, silver and gold upon Sattin in several forms or figures, as several flowers, the sensitive motions streight by one and the same act, pattern out all those several figures of flowers, as also the figures of Silk, Silver, Gold and Sattin, without any pressure of these objects, or motions in the medium, for if they all should press, the eye would no more see the exterior objects, then the nose, being stopt, could smell a presented perfume.
Thirdly, They may ask me, if sight be made in the eye, and proceeds not from the outward object, what is the reason that we do not see inwardly, but outwardly as from us? I answer, when we see objects outwardly, as from us, then the sensitive motions work on the outside of the organ, which organ being outwardly convex, causes us to see outwardly, as from us, but in dreams we see inwardly; also the sensitive motions do pattern out the distance together with the object: But you will say, the body of the distance, as the air, cannot be perceived, and yet we can perceive the distance; I answer, you could not perceive the distance, but by such or such an object as is subject to your sight; for you do not see the distance more then the air, or the like rare body, that is between grosser objects; for if there were no stars, nor planets, nor clouds, nor earth, nor water, but onely air, you would not see any space or distance; but light being a more visible body then air, you might figure the body of air by light, but so, as in an extensive or dilating way; for when the mind or the rational matter conceives any thing that hath not such an exact figure, or is not so perceptible by our senses; then the mind uses art, and makes such figures, which stand like to that; as for example, to express infinite to it self, it dilates it parts without alteration, and without limitation or circumference; Likewise, when it will conceive a constant succession of Time, it draws out its parts into the figure of a line; and if eternity, it figures a line without beginning, and end. But as for Immaterial, no mind can conceive that, for it cannot put it self into nothing, although it can dilate and rarifie it self to an higher degree, but must stay within the circle of natural bodies, as I within the circle of your Commands, to express my self
Madam,
Your faithful Friend,
and obedient Servant.
XXI.
MADAM,
Heat and Cold, according to your Authors opinion, are made by Dilation and Contraction: for says he,[1]