Philosophy 167: Class 9 - Part 5 - Celestial Motion in Vortices: Descartes' Copernicanism, and His Definition of Movement.

Smith, George E. (George Edwin), 1938-

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Synopsis: Descartes supported a Copernican model over Tychonian, and defined movement as a relative motion rather than absolute.

Philosophy and science.
Celestial mechanics.
Descartes, Rene, 1596-1650. Principia philosophiae.
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All right, his Copernicanism is fairly easy to explain, that these are his diagrams. You'll how see how striking the orbits are in the Copernican system. They are not circle. They are most noticeably not a. Evenly spaced. I think they have the character of a complex vortex, to say the least.
And then the one on the right is the Tychonic system. And his initial argument is that the one of the left is enormously more simple, and of course it is from the point of view of vortices. Think of what the one on the right has to do. There is a gigantic vortex around the sun, carrying all of the planets except the earth.
Within the body of that vortex is the earth creating another vortex that's carrying the sun and all the planets around it. And nobody's ever seen a vortex like that. He doesn't mention, though the drawing has it right, he doesn't mention that on the Tychonic system the two inner planets, Mercury and Venus, are going in the opposite direction.
How the vortex around the sun is supposed to drive Mercury and Venus in one direction, and the outer planets in the other direction. Again, vortices aren't gonna do it. So if you conclude that the planets are being carried, known planets are being carried by vortices, it's pretty much out of the question that the Tychonic System is even a candidate.
Okay, is it at least nice why he sees fairly clearly it can't be, can't be Tychonic? We've now got three arguments for the Copernican over the Tychonic system, Kepler, Galileo, and Descartes. They're all different. Two of them are based on physics, Galileo's is based on the tides. Now the obvious problem is how does he reconcile this with scripture.
Now, Descartes was a very serious Catholic. He withheld Le Monde so that he would not be put under house arrest. Of course, he was living in Holland so he had no real danger of house arrest, but I think he really wanted his writings to take over all the universities.
That is, and by the way, at least one university, I think it was Utrecht, adopted a pure Cartesian curriculum for a period of years. Which was his great hope, that all the universities would switch from scholasticism to the Cartesian. So he's got a problem with the Church and his way of handling it, didn't want to do that, glad I had the top on it.
That the earth properly speaking, is not moved. Nor are any of the planets, although they are carried along by the heavens. And it's important to remember here what was said earlier considering the nature of movement. That is that if we are speaking properly in accordance with the truth of the matter, it is only the transference of a body from the vicinity of those bodies, which are immediately contiguous to it, and considered to be at rest into the vicinity of others.
However, in common usage, all action by which anybody travels from one place to another is often called movement. In this sense of the term it can be said that the same thing is simultaneously moved and not moved according to the way we diversely determine it's location. That's relative motion, in relative motion there's an arbitrariness about which things and which not, that's what it's referring to.
From this, it follows, typo, it follows that no movement in the strict sense is found in the earth. Or even in the other planets because they are not transported from the vicinity of the parts of the heaven immediately contiguous to them and as much as we consider those parts of the heavens to be at rest.
For it to be thus transported they would have to be simultaneously separated from all the contiguous parts of the heaven which does not happen. However, because the matter of the heaven is fluid, sometimes some of it's particles and sometimes others move away from the planet to which they are contiguous.
And this by a movement, which must be attributed solely to them and not to the planet in the same way as the partial transference of water and air which occur on the earth's surface, etc. Okay, that's rain he's talking about. And then we flash back to what I skipped last week, 225, I mentioned it at the end.
The definition of movement properly speaking. If, however, we consider what should be understood by movement according to the truth of the matter rather than in accordance with common usage. In order to attribute a determinate nature to it. Now pause on that. In order to attribute a determinate nature to it.
Okay, if there's only relative motion, there's no determinate attribution of motion to any one object. It could be the two are moving relative of one another. One moving the other stationary, etc. That's what he's referring to. Knows the phrase, though, determinate nature to it. We can say that is now these are my italics.
The transference of one part of matter, or one body, from the vicinity of those bodies immediately contiguous to it and considered as at rest into the vicinity of others. By one body or part of matter I hear understand everything which is simultaneously transported. Even though this may be composed of many parts which have other movements, etc.
I also say that it is a transference, not the force or action which transfers, in order to show that this motion is always in the moving body and not in the thing which moves it. And finally, he says at the end, I have also added that the transfers of the affected from the vicinity of those bodies continuous into the vicinity of the others, not from one place to another.
Now that's going to be a big deal. And then third to last week, you'll read Newton outspokenly attacking this and showing you don't get a determinant quantity of motion at all. And it's what leads into Newton worrying about relative versus absolute motion, et cetera. It's very much this passage.
Newton treats the passage as if it's pure subterfuge on the part of Descartes. He's found a way to sneak himself, sneak his doctrines past the Church without getting into trouble. And that may be the case, some scholars say Descartes never took those proposals seriously, other think to the contrary and took it totally seriously.
He thought he had found the answer. I have no idea how to react to that. There's nothing like this in Le Monde. I read the Le Monde passage to you last time, movement is transferred from one place to another. But it does raise an interesting question, how do we distinguish true motion from what is not true motion?
But of course he gives us something later in part two, which the forces that tell us. Okay. Though he doesn't develop that here.