Philosophy 167: Class 9 - Part 10 - The Conclusion of the Principia: Five Principles that Establish the Absolute Certainty of Descartes' Physics.

Smith, George E. (George Edwin), 1938-
2014-10-28

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Synopsis: The conclusion of Descartes' Principia argues that his methods prove his theory.

Subjects
Astronomy--Philosophy.
Astronomy--History.
Philosophy and science.
Descartes, Rene, 1596-1650. Principia philosophiae.
Genre
Curricula.
Streaming video.
Permanent URL
http://hdl.handle.net/10427/012784
Original publication
ID: tufts:gc.phil167.97
To Cite: DCA Citation Guide
Usage: Detailed Rights
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All right what I'm going to end with from the book. And it's gonna be a discussion of Descartes science but picked up initially from what Descartes himself says in the last I guess it's six or seven Already calls in book four, than in the whole book. They're kind of remarkable in some ways cuz they make progressively stronger claims.
So, let's start, I'm gonna read the whole of this one, this starts the series. Notice the topic. Imperceptible particles of bodies exist. I also consider in individual bodies many particles which are not perceived by sense. Which may not be approved by those who take their senses as the measure of the things we can know.
Yet if only he considers what is added each hour to those bodies which are gradually being increased, or what is removed from those bodies, which are being decreased, who can doubt that there are many bodies so tiny that we do not perceive them by our senses? I simply remind you of a Philosophy one rule any argument that takes the form of a rhetorical question is not an argument.
Okay. Nor do I think that anyone who is using his reason will be prepared to deny that it is far better to judge things which occur in tiny bodies, which escape our senses solely because of their smallness on the model of those which our senses perceive occurring in large bodies.
Than it is to devise, I know not what new things, having no similarity with those things that are observed. In order to give an account, explicando, again, of those things. Now again, I invoked Michael Schneider earlier. One of the points he makes in his senior essay is Descartes was saying the Physics of the Earth extends to the heavens.
That's fair, right? It extends to everything and he's saying it here the reverse. You don't say this, it extends to the microscopic. Now why? Because what's the alternative? If it doesn't we haven't got a prayer. Right? If the Physics of, if Microphysics laws that we have no resemblance to what we can observe we're in a lot of trouble to get the laws of Microphysics.
It's fairly amazing that they actually do differ the amount they do and we finally got to them. But that's a story for a different course, a course centered on the early 1920s now jumping to 203. How do we know the figures and movements of imperceptible particles? But I attribute determined figures and sizes and movements to the imperceptible particles of bodies as if I had seen them.
Now, the word determine means definite value, definite shape, definite size, definite motion, et cetera. Some readers may perhaps ask how I therefore know what they are like, to which I reply, that I first generally consider from the simplest and best known principals, the knowledge of which is imparted by nature.
What the principal difference is in the sizes, figure and situations of bodies, which are imperceptible, solely on account of their smallness could be, and what perceptible effects would follow from their various encounters. That's a strong claim. Let's take all the possibilities of what could be happening at the Microphysical level and ask whether they produce Macrophysical effects.
Now, that's not too far removed from what happened with Kinetic theory and Atomic theory. At the time, everybody was saying molecules are spheres. And as a result, they were getting very poor in numerical agreement with a lot of things, but that was the picture they were having, and they were trying to generate everything out of the movement of.
So, it's not something we didn't do at a later point. And next, when I noticed some similar effects in perceptible things. I judged that these things had been created by similar encounters of such imperceptible bodies, especially when it seemed that no other way of explaining these things could be devised.
That's my emphasis added, no other way of explicating these things could be devised, except this one and of course the way you get that is having so many things come out of a single thing. Natural effects almost always depend on some devices so minute that they escape our senses.
And they are absolutely no judgments in mechanics which do not also pertain to Physics, of which mechanics is a part or type et cetera, well, let's finish, it's a nice thing. Accordingly, just as when those who are accustomed to considering Automata know the use of some machine and see some of its parts, they easily conjecture from this how the other parts, which do not see, which they do not see, or may, et cetera.
What you probably don't know was a big deal at the time to make Automata and a clock like fashion, things that would move, arms, et cetera, he'd wind them up and it was big form of entertainment. So at any rate, that's the reference and of course the striking thing to me is what I italicized.
No other way of explicating these things could be divised. Earlier he said no other way could be imagined, those things are slightly different, they can be divised, in 204. That is suffices if I explain what imperceptible things may be like even if perhaps they are not so. And although perhaps in this way it may be understood, and there's the word I wanted before intelagotora, how all natural things could have been created, it should not therefore be concluded they were, in fact, so created.
He's not going to say what God did, right? That's what really gets you in trouble with the church. And indeed, I most willingly concede this to be true, and will think that I have achieved enough if those things which I have written are only such that they correspond accurately to all phenomenon in nature.
And indeed this will also suffice for the needs of everyday life because medicine and mechanics and all other arts which can be perfected with alpha physics has as their goal only those affects which are perceptible and which accordingly ought to be numbered among the phenomenon nature. So he's made a model and now he's saying, hey if it's just as if the world were this way because we can draw all the practical conclusions we want out of it even if it's not really this way, if of course it's exactly as if it were this way.
You'll see that same move being made by Maxwell. Cameron is not here tonight, but when Maxwell starts talking about his fluidic models of electricity, he actually uses phrases as if, and it's gone into the model literature now as if models. That those things which I have explained here do seem at least morally certain however.
Now morally certain means certain for all purposes of human action. Okay. Not Certain, by God, by all purposes of interaction. So unless some injury to truth may occur here, it must be considered that there are things which are held to be morally certain, that is to a degree which suffices for the needs of everyday life.
Although if compared to to the absolute power of God, they are uncertain. Thus, for example, someone wishes to read a message written, that is encrypted, in Latin letters, to which their true meaning has not been given. And if upon conjecturing, this is all brackets, the key to the cypher, he finds by this means, certain Latin words are formed by these letters.
He will not doubt that the true meaning of that message is contained in those words even if he knows that solely by conjecture and even though it may be the case that the person who wrote the message did not follow that key, but some other. And thus concealed a different meaning in the message.
Not long ago Dan tried to push me to agree to certain claims about, happen to be about evolution. Purely on the grounds that it's using this same metaphor. Take a cypher, you come up with one that works, doesn't that make it extremely probable? Isn't it irrational not to believe it, et cetera.
I don't know if Dan realized he was using something he had seen in Descartes when we taught a jointly, it's a good question. It would however be so difficult for this to happen to be wrong about such a message. That it does not seem credible but those who notice how many things concerning the magnet fire and the fabric of the entire world have been deduced.
That's an interesting word, deduced here from so few principles, even though they may suppose these principles only by chance and without reason will perhaps still know that it could scarcely have occurred. That so many things should be consistent with one another if they were false. And then finally, I think this is the last of them, that on the contrary, they seem more morally certain, okay?
That's the last line on the whole thing. Having started, they may be totally false, but they'll be okay as if. And we go, well, they're really morally certain and now they're gonna be more than morally. Besides there are, even among natural things, some which we judge to be absolutely and more than morally certain, basing our judgment on the metaphysical foundation that God is supremely good and by no means deceitful.
And that accordingly the faculty which he gave us to distinguish the true from the false cannot err when we use it correctly, and perceive something clearly with it's help. Now, of course, the appeal there is to the meditations. Such are mathematical demonstrations, such is the knowledge that material things exist, and such are all evident demonstrations which are made concerning material things.
Again, meditations in mind. These reasonings of ours will perhaps be included among the number of these absolutely certain things by those who consider how they had been deduced in a continuous series from the first and simplest principles of human knowledge. Especially if they sufficiently understand that we can feel no external objects unless some local movement is excited by them in our nerves.
And that such movement cannot be excited by the fixed stars very distant from here, unless some movement also occurs in these and the whole intermediate heaven. For once these things had been accepted, it was scarcely seen possible for all the rest, at least the more general things, which I have written about the world and the Earth to be understood otherwise than I have explicated them.
And I just throw out and then I'll throw open for this. I'm gonna make some comments, give Patrick a chance to reply. The distinction here from the dictionary between explana. For those who don't know Latin explana, explano is the first person singular conjugation. I explano, okay. Explanare is the infinitive and that's the way you normally give Latin verbs is the first person present singular followed by the infinitive.
And I'm just giving you, reading out this is not the big thick dictionary in my office, it's just a student dictionary, but the difference between exploco, explecar, and expleno explenare is fairly dramatic. It's that's being used all throughout. There's a third one, and that the is X positive so the word we get out of that is to exposit.
So you can explain, you can explicate, you can exposit, okay? The three are different in Latin and it's not clear the English mirrors those three but the three are used differently and both Newton, Newton never use the verb explorare in any edition of the Principia or in any of the notes he makes in the editions.
It's always either explonara or explocare and Descartes throughout is using explocare. Now what you wanna make of that I don't know but I just don't think, I think that blindly translating it explain is just saying it's fitting into 20th. It's a 20th century reading of the work because explanation has become so central on science today.
It's not absolutely clear. That's what he meant because he's explicating how things work, to a very great detail.