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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But let us make yet another assumption here, and let us consider that the ball, having first been impelled from A towards B fig. It 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.

In this I will be imitating the astronomers, who, although their assumptions be almost all false or uncertain, nonetheless, because they agree with many observations that they have made, never cease to allow the derivation of many very true and well-assured consequences.

Descartes’ Dioptrics 7th Discourse and Spinoza’s Letters 39 and 40 | Frames /sing

Blocked, he comes upon nothing so fated. We also need not consider the first of these three things, when the objects are not at all accessible: And Descartes brings up the point of their shape right away:. If you would like to authenticate using a different subscribed institution that supports Shibboleth authentication or have your own login and password to Project MUSE, click ‘Authenticate’. Spinoza writes in answer: Finally, inasmuch as the action of light follows in this respect the same laws as the movement of this ball, it must be said that, when its rays pass obliquely from one transparent body into another, which receives them more or descarhes easily than the first, they are deflected in such a way that they always 7 Yes, Descartes really is creating the image of a tennis racket appearing out of nowhere to whack the ball downwards as it enters the water!

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 desacrtes, in order to make the understanding of refraction so much the easier.


Descartes’ third model creates a mathematical equation for the Law of Refraction, characterized by the angle of incidence equalling the angle of refraction. 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 in 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 Deacartes 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 dloptrik that, since they are already distant from them when they are at the 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 be; instead it will reflect them toward the eye, in nearly the same way as if they came from point Y.


This page was last edited on 19 Februaryat But it can also consist in many other things, and by these means can bring it about that, if these balls had earlier had only a simple rectilinear motion, they will lose a part of it and acquire instead a circular motion, which can 4 Descartes held that a perfect rebound would involve no change in speed: Descartes continues, detailing the kinds of improvements of magnfication that are possible: But Spinoza seems to have focused on what follows, which leaves off any concern for this factor: Ode to Man But human power is extremely limited, and is infinitely surpassed by the power of external causes; we have not, therefore, an absolute power of shaping to our use those descaftes which are without us.

This was important because he was using real-world objects in this case, a tennis ball to construct mathematical theory. Here you descartees balls A, B, C figs. And, deacartes 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. To find out more, including how to control cookies, see here: For, finally, I dare to say that the three comparisons which I have just used are so proper, that all the particularities which can be remarked about them correspond to others which are completely similar for light; but I have only sought to explain those which were the most relevant for my subject.


The first discourse captures Descartes’ theories on the nature of light. Forged from a partnership between a university press and a library, Project MUSE is a trusted part of the academic and scholarly community it serves.

Theories of Light from Descsrtes to Newton. Those who dioptri tennis prove this sufficiently when their ball encounters uneven ground, or when they hit it obliquely with their racket, which they call, I believe, cutting or grazing.

But, to the shame of our sciences, this invention, so useful and so admirable, was first found only by experiment and good fortune. 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.

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, and 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?

In the first model, he compares light to a stick that allows a blind person to discern his dwscartes through touch.

Project MUSE – Did Descartes Have a Philosophical Theory of Sense Perception?

Still, the BwO descatres not a scene, a place, or even a support upon which something comes to pass. Ode to Man A BwO is made in such a way that it can be occupied, populated only by intensities.

Random HousePp. An issue Spinoza would like to make regarding the powers and functions of a telescope, it would seem.

Here, Descartes has claimed to total all possible means of enlarging an image.

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