let's come to Descartes physic, talk about philosophy, I told you about the book the Descartes wrote “Principles of philosophy” and finally abandoned in the world remembers the title, that the world or a treatise on light。

the world or a treatise on light, what is it about, this is about the way the world can be produced in all details the world can be produced through mathematical laws applied to matter.

this is a cosmogony, that is to say the detail of the formation of the world, that is the goal of Descartes to explain how it is possible to understand the world, as a result the effects of the this application of the laws to matter, so we begin with the matter without any form, and when the law of nature are applied to this matter progressively, a world will be formed, that is what Descartes pretence, and that is what he wants to show, what he wants to explain is designed as the general order of phenomenon.

we start with the matter without form, and we have to come to the general order of phenomenon at the appearance, that is his goal in physics.

in physics he considers that it is possible to explain so old phenomenon as the order of this phenomenon is in the world, by starting to consider only matter to matter, and in those in nature and progressively, he considers a world will be formed, that is what he wants to explain.

he choose to present this in fable and he did, he is very precise on it, these great hypothesis on the formation of the world of the world is presented as a fable.

It's not the truth, It's only a fable, in the principles with the supposition of the astronomers, of course, you see an important difference, the civilizations of the astronomers do not pretend to achieve the causes, that only describe the movements and they are consenting in order to predict these movements.

but Descartes not deal with the causes, Descartes favorite is quite different, what he pretends is that he can explain deformation all of all this world considering certain closes, that is to say the law of nature, but despite of these difference, he compares his work his fable with the supposition of the astronomers, because he assumes that this is entirely, in some sense this is entirely face. this is entirely first you will see why, this is entirely false, but this is useful to understand the way mechanics is at work in the world, the way mechanics produces all the phenomenon, so I want explain you the detail of the book, Descartes, abundant in thirty four.

I prepared something like this, I would give it to you， if you want but I want to come directly to the most important presentation given by the Descartes， this presentation is in of course the principle of philosophy, a summary of the principles are there four parts.

one about metaphysic, the second principles of material things, so we come to physic, principles of material things, a very important text in which Descartes, invented important concepts of the modern science, for instance in these text, Descartes introduces a principle of conservation principle of conservation.

it's quite important and in this part he discovers the laws of nature, the laws of nature.

the third part he's about the way the visible world can be produced through the application of those laws to the matter, so three part, the visible world, here begins the fable, the fiction.

and the forth path is the earth, so the sky discern the planet celestial bodies, and then the earth.

so all this is conceived as a fiction offence supposition.

I would like it does anyone of you, yes please could you give me your book just for one second, your book, that's it I want, the page don't worry.

the principles of philosophy of Descartes are a very long book, but like this and if I consider this summary, and project it on the book, do you realize that what is designed as figure by the Descartes is all this ?

two parts here, and the explanation of the formation of the world, which is a several fiction represents this, so this is very important.

the fact is that in the world or a treatise on light, Descartes was talking of a fable, but this dimension of fiction did not disappear in the principles of philosophy, quite the contrary quite the opposite in fact.

the third part of the principles of well, the text I will show you now send you after belong to the third part of the book.

the third part of other principles which takes up the aim of a general cosmogony formation of the world, the third part actually gives affective attitude to this explanation more clearly than in the other books or text of the Descartes.

I will show you, these remarkable declaration of the Descartes, and I am so eager for readers to believe everything I write, that I show even put forward to some things, that I believe to be outright face things that I believe to be outright face.

and of course this following article precisely specifies is that it would be about two positions.

so let's examine the question of supposition, read at the beginning of this section, about the physical world dedicated to the physical world, it would be those beneficial to consult Spinoza to consult, Spinoza also gain, because he provides the best commentary of the Descartes, he was a wonderful reader, and he bought his first book, the first book of Spinoza is principles of philosophy of Descartes.

I don't no confusion Descartes wrote principles of philosophy, Spinoza principles of principle of Descartes, so he in this book, Spinoza indicates that the hypothetical aspects of the Descartes is not only the description of the astronomical phenomenon, which is only a an abstract supposition phenomena, now It's everything that fellows everything is disconcerted by the Descartes as a fable.

the problem is to collect principle such as and that is the sense of these fables,, such as listen carefully Spinoza, we demonstrate that the finished the body, the earth, and finally everything we discern in the visible world, could have come like seeds even though we know full well that they did not come from.

then so we will consider everything we see, everything that appear in the visible world as if they came from seeds, as it became from like seeds, we know it does not have one happen like this way, didn't happen like this way, in other words, the Descartes general hypothesis is across mechanic fiction, of a fable on the world, a cosmogenic fiction or a fable on the world.

Descartes himself really uses this term stable several times into correspondence in his letters about the principles of philosophy, so what I would like to show you, if that the fictional narrative it is a narrative, but It's not anymore a narrative about a spirit about the common spirit searching for truth.

It's a narrative about the world, and this fictional narrative does not constitute a simple packaging, or a noble act presentation of a certain conception of physical world, but the way Descartes uses fiction is much more connected to the description of rational list, reduction list, mechanist hypothesis on phenomenon, so that is what I want to show you.

fiction is not only fable, is not only some kind of package, it is deeply connected with id, with the project of the reduction list mechanized explanation of phenomenon that is the important point.

that is the important point I want to show you, you see It's not only a matter of presentation of the cells of Descartes, you will see it is deeply connected to his scientific project.

I tell you, what do I mean by a reduction estate here, what do I mean by this the cut is only considering matter on a very simple way, according to the Descartes, matter is only and only the extension, you see the fact that matter occupies a certain place, that's all the matter Descartes considers, in fact is the same that is considered.

so what does he give to himself in order to produce this explanation matter, and the laws of nature, the laws of nature, they are not plenty of laws in decades philosophy, there are three laws of nature.

the first law and the second, one form is a principle of inertia, there is no strictly talking there is no principle of inertia designated as such by the Descartes, but the first two laws constitute such a principle of inertia, and the third law It's about the shock between bodies, material bodies and that's all what Descartes pretends is that considering only this matter without any form.

the application of those laws to it is possible to explain the production of the world we see, that is of course reduction list method that is what I meant, is that clear?

I’m not Descartes is presenting its like this way, you're perfectly right to be sure is that kind of method to analysis especially to analysis present to an analytic presentation, you're perfectly right.

I will talk about this later, if you don't mind, we'll come to this later, but you are right but the point is that Descartes is far more interested in presenting his project as a federal fiction, then in telling us, if it is analysis or synthesis, so you're right but I shock and not inventing some fiction, Descartes is considering for reasons, you will discover right now, is considering that old this can only be fiction.