At any rate, let's turn to the book itself. This is the title page in English, as translated by Bill Donahue. You are simply now seeing what you saw before in Latin and Greek. The book consists of five part 70 chapters. Part one is an argument that the tradition dating all the way back to Hipparchus of referencing the mean sun, instead of the visible sun, the true sun, the actual sun that that's a serious mistake we need to replace the mean sun with the actual sun.

And, as part of that, he shows if you do so, we appear on initial basis to solve the problem of latitudes, once and for all. So, that's what part one does. It introduces two major reforms. One for actual sun versus mean sun. The other for the latitudes. He needs the latitudes for an argument later, that's why he does it early on.

Part two, which is the next page. Part two is, quote, "an imitation of the ancients". He adopts a column A type deferent orbit, that is an eccentric with an equant and does the best he can to approximate Mars with the observations of Tycho. We'll look at that in some detail.

And what he comes up with he calls his vicarious theory. It's a theory that gives very accurate heliocentric longitudes for Mars, but it's definitely a false theory and one of the chapters in that If you look carefully, he has to explain how a false theory can nevertheless give good longitudes, and he takes the trouble to do that very typical of him.

He's always gonna do that sort of thing. Part three, and there I've actually singled out part of it, for reasons I'll get to in a few minutes. The earth-sun orbit is different from all of the other Ptolemaic orbits. It does not have an equant. Or, it has an equant, it's at the center.

And so it doesn't have bisected eccentricity. He has physics reasons for wanting bisected eccentricity. So he asked the question, is the earth-sun orbit also got bisected eccentricity? And you'll see the chapters run from 22 to 40, that's 18 chapters working out that it does. And it ends with the area rule as an approximation to another rule.

Part four, then, which is the top of the next page, part four is what he's famous for, working out the ellipse. And it runs from chapter 41 through chapter 60. That's 20 chapters. It's interesting, you'll see when we get to it. He does not ever hypothesize an ellipse.

He actually resisted, for almost two years, going to an ellipse when it was staring him in the face. Okay, so this is not something where he had the clever idea it's an ellipse, he took real pressure from the data to force him into the conclusion it's an ellipse.

That's one of the more fascinating things here. Curtis Well said in the articles I gave you Is more focused on he discovered it and less focused on some of the arguments, so I'll be supplementing that and then part five is on the latitudes. He comes back and once he has all the longitudes, he can do the latitudes much more precisely.

So we just wrapped that up. Two things about this. I'm about to really shock you with the next slide. Before I get to them there is in the translation of the original runs 20 pages. And the translation it runs 30 pages. A one paragraph summary of all 70 chapters before you start the book.

Because he knows how hard the book is to read, okay? But more dramatic than that, before the summary, is he gives you an outline of the book. The structure of the argument. And how each piece in each chapter fits in to the point at the far left. And this runs four bloody pages.

Okay. That's how hard the argument is. The argument goes all over the place. Constantly converging on main points in each part. One last thing and I'll pick up the question from David. He presents this as if this is the pattern by which he discovered things. Jim Vocal and his dissertation went off to St. Petersburg.

For those who don't know, it's always a nice story. Catherine The Great, the great German queen of Russia. I once had a Russian student in this class referred to Catherine the Great of Russia and she screamed at me. She wasn't Russian! But she was of course German. Voltaire convinced her to go out and buy all valuable scientific manuscripts that she could get ahold of.

So all the Kepler papers sit in St.Petersburg of all places because she bought them and they're there. Vocal Wanton Lupton kept all of Kepler's notebooks. Kepler is in effect revising the path that he actually followed in order to give a kind of narrative argument to readers to persuade them what Vocal says rhetorically.

A rhetorical move to convince them of the evidence origin. So I hope I've convinced you this is a very, very difficult book to follow. The best I can tell and I tried and tried on this. This book convinced exactly one person, Kepler. I can't find anybody in the history of astronomy in the 17th century.

It's hard enough to find anybody who read this book. Okay? Newton definitely didn't read this book. Kepler's most important follower Jeremiah Horax definitely did not read this book. So, we're in the funny position that we can't find anybody who actually went through the argument and came to understand it except Kepler himself.

That doesn't mean the argument didn't contribute to science, because of course, once Kepler had the argument this way, as you'll see next week, he gives you the argument two other ways. So, I don't want to suggest the argument isn't worth going into. All right, any questions on that?

If not, I'm going to actually start going into the details. I thought you would be struck by that outline. I mean, it's no really an outline. It's a flowchart believe it or not. Flowchart of reasoning. And you have it you can look at it and see yourself whether you can make any heads or tails of it.

By the way, it's a sad thing, Cambridge University Press did not keep this book in print, so it's out of print after 10 years of hard work by Donna Hugh to translate it. I gather it's out of print at the present moment. And they actually remainder all the copies and once they did that he asked for them so he's given all of his copies out now and there are no more.

I hope that's not true of Cambridge Press because I publish with Cambridge Press and I don't believe they're that bad.