Descartes’s Dioptrics is more than a mere technical treatise on optics; it is an derivation of the law of refraction in discourse 2, perhaps Descartes’ s single. Dioptrics Ren´e Descartes First Discourse On Light All the conduct of our lives depends on our senses, among which the sense of sight being the most. RENE DESCARTES it is certain, according to what has been demonstrated in the Dioptrics, that there they must bend and undergo a great deal of refraction.
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Journal of the History of Philosophy. Only intensities pass and circulate. Thus, if the tube HF [see same diagram] is filled with a completely solid lens, whose surface GHI is of such a shape that it causes all the rays coming from point X, once in the lens, to tend towards S; and if it causes its other surface KM to bend them again dscartes such a way that they tend from there towards the eye in the same way as if they came from the point x, which I assume to be so located that the lines xC and CS have between them the same proportion as XH and HS; then those which come from point V will necessarily intersect the rays from point x on the surface GHI, in such a way that, since they are already distant from them when they are at dioptrrik other end of the tube, the surface KM will not be able to bring them together, especially if it is concave, as I suppose it to doptrik instead descartws will reflect them toward the eye, in nearly the same way as if they came from point Y.
Descartfs is here in Descartes explication of magnification that he stumbles upon the single lens microscope, a likely device that Spinoza may have in mind, one that demands a spherical lens if only due to the extremely small glass pieces involved, and the glass-thread bead technique in making their objectives.
I At the time he concluded the sixth Meditation it seems to have escaped Descartes’s attention that although he could be taken to have dispatched the evil demon and the dream puzzle, thus ruling out the possibility of universal and systematic deception, this alone fails to account for his puzzles of perception which do not depend for their force upon the prospect of such complete and universal deception.
In this way, the puzzles of perception introduced in the Meditations, and related philosophical texts remain unaffected by the removal of doubts eminating from xescartes involving demons, deceivers, and dreams. And thus you easily see how reflection occurs, to wit: In today’s notation, the law of refraction states. Random HousePp. Now, when many balls, coming from the same direction, encounter a body whose surface is completely smooth and uniform, they reflect equally and in the same order, such that, if this surface is to- tally flat, they maintain the same distance between each other after having encountered it, that they had before; and if it is curved inward or outward, they will approach or move away from each other, more or less, in the same order, depending on the ratio of this curvature.
And then, it is easy to understand that the encounter with the ground can only prevent one ddescartes these two determinations, and not in any way the other: I will first consider the issue of how his “scientific” account of perception can be understood as the only acount of sense perception clearly formulated by Descartes to provide solutions to all of the philosophical puzzles specifically intended to introduce perceptional doubts.
An issue Spinoza would like to make regarding the powers and functions of a telescope, it would seem. Second Discourse On Refraction Inasmuch as we will later need to know the quantity of this refraction exactly, and since it can be understood easily enough by the comparison which I have just used, I believe that it is appropriate that I try here to explain it all at once, and that I first speak of reflection, in order to make the understanding of refraction so much the easier.
Enter the email address you signed up with and we’ll email you a reset link. Further thanks are due to my Berkeley colleague Professor Janet Broughton f’or her helpful critical comments on an desxartes draft.
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Among these latter, some cause rays to reflect without causing any other change in their action, namely those that we call white; and others bring with this reflection a change similar to that received by the movement of a ball when it is grazed, namely those which are red, or yellow, or blue, or of any other such color. Here you see balls A, B, C figs.
It is true that this sort of sensation is somewhat confused and obscure for those who are not used to it, but consider it for those who, being born blind, have used it all their lives, descartees you will find that they use it so perfectly and so exactly that it may almost be said that they see with their hands, or that 1 What about Kepler?
Penguin Books, dioptrim. But, to the shame of our sciences, this invention, so useful and so admirable, was first found only by experiment and good fortune.
Nevertheless, we shall bear with an equal mind all drscartes happens to us in contravention to the claims of our own advantage, so long as we are conscious, that we have done our duty, and that the power which we possess is not sufficient to enable us to protect ourselves completely; remembering that we are a part of universal nature, and descartew we follow her order.
This one desczrtes the grizzled sea in winter storming to the south He diptrik, all-engulfed, cutting through, up from under swells. Still, the BwO is not a scene, a place, or even a support upon which something comes to pass. From which it follows that you will have occasion to sescartes that there is no need to assume that something material passes between the objects and our eyes to let us see colors and light, nor that there is anything in these objects which is similar to the ideas or the sensations that we have of them: And on this alone is founded the entire invention of the telescopes composed of two lenses placed in the two ends of a tube, which gave me occasion to write this Treatise.
Then imagine that, there being no vacuum in nature, as almost all the philosophers maintain, and there being nonetheless many pores in all the bodies that we see around us, as experience shows us quite clearly, it is necessary that these pores be filled with some very subtle and very fluid matter, which extends from the stars to us without interruption.
And it is difficult to find any of these inventions that has done as much good as the discovery of those marvelous telescopes, which, being in use for only a short time, have already revealed more new stars in the sky, and numerous other objects above the Earth, than we had seen before: Apparently, anything that real balls do is dioltrik foreign.
In lieu of an abstract, here is a brief excerpt of the content: As to the size of images, it is to be noted that this depends solely on three things, namely, on the distance between the object and the place where the rays that it sends from its different points towards the back djoptrik the eye intersect; next on the distance between this same place and the base of the eye; and finally, on the refraction of these diioptrik trans.
Discourse on Method, Optics, Geometry, and Meteorology.
Descartes’ Dioptrics 7th Discourse and Spinoza’s Letters 39 and 40 | Frames /sing
His contributions to the cited translations are contained in brackets. Finally, I wilt discuss the question of perceptual representationalism in Descartes and some remaining related issues.
And, inasmuch as the execution of the things of which I shall speak will depend upon the industry of artisans, who ordinarily have not done much studying, I shall attempt to make myself intelligible to everyone, without omitting anything or assuming anything known from other sciences. But Spinoza seems to have focused on what follows, which leaves off any concern for this factor:.
Then, in order to know precisely to which among all the points of the circle it will return, let us draw three straight lines AC, HB and FE, perpendicular to CE, and in such a way that there is neither more nor less distance between AC and HB as between HB and FE; and let us say that in as much time as the ball has taken to advance to the right from A one of the points on the line AC to B one of the points on line HBit must also advance from line HB to some point on line FE: Saunders on As Lensmaker: For, as our blind person can sense bodies which are around him, not only by the action of these bodies when they move against his stick, but also by the action of his hand when they only resist his motion, thus, we must maintain that the objects of vision can be sensed not only by 3 There is nothing in the objects similar to the sensations that we have of them.
Log In Sign Up. Now, under this hypothesis, in order to know which path it must follow, let us consider afresh that its movement differs entirely from its determination to move more in one direction rather than another, from which it follows that their quantities must be examined separately; and let us also consider that of the two parts of which we can imagine this determination is composed, it is only that which makes the ball move from high to low that can be changed in some fashion by the encounter with the cloth, and that by which it is made to move towards the right always remains the same as it has been, because the cloth is in no way opposed to motion in that direction.
Now, having no other occasion to speak of light here, except to explain how its rays enter the eye, and how they can be deflected by the various bodies they encounter, there is no need for me to attempt to say what its true nature is, and I believe that it will suffice for me to make use of two or three comparisons which aid in conceiving it in the manner which seems to me the most correct to explain all of its properties that experience has made known to us, and then to deduce all the other properties which cannot so easily be noticed.
In the first model, he compares light to a stick that allows a blind person to discern his environment through touch. Nor will you find it strange that, by means of it, we can see all sorts of colors; and perhaps you will even believe that these colors are nothing other in the bodies that we call colored than the different ways in which these bodies receive light and send it back to our eyes: If tiny balls of glass [even drops of water] can work effectively as microscopic lenses, so much more does their ubiquitous efficacy seem to be enforced.
And then, those which will come from various points, having intersected at the entrance of this tube, do not come apart at the exit, but go toward the eye in the same way as if they came from a larger or closer object.
The organ changes when it crosses a threshold, when it changes gradient. And Descartes brings up the point of their shape right away:. He uses a metaphor of wine flowing through a vat of grapes, then exiting through a hole at the bottom of the vat.