So, this is the rest of his life. The decree of the Congregation of the Index prohibits Copernicus' De Revolutionibus until corrected and made more hypothetical. So, they went in, they changed the book. A few years later, it was okay to read it. It remained on the Index until the 19th century, the original.

That is, it was a sin to read the book if you were a Roman Catholic in the original, unless you got dispensation from your priest. Judge that for what it's worth yourself. The great comets stir up discussion. I'll come back to that. Galileo gets into a fierce controversy publishing under the title of his disciple, not under his own name.

You see, in 1620, Copernicus's work is reissued. Now, 1621 is a major moment because Pope Paul and Cardinal Bellarmine die, as does Grand Duke Cosimo. So the person to whom Galileo made a promise not to do Copernicanism anymore died. Pope Paul V, who was the person who pushed the issue of Copernicanism, he's died.

And Galileo no longer has the full protection of the Grand Duke. His replacement, Ferdinand, they never had the same relation that Galileo had to Cosimo, cuz Cosimo had been his tutee. What follows right away, 1623, Maffeo Barberini is elected Pope and takes the name Urban VIII. He was the cardinal of Florence.

And then those knights I'm describing in the Medician Palace, which still stands in Florence. You should, if you get to Florence, that's one of the things to go see. He was always present at these disputations, and he loved listening to Galileo argue and win his arguments, etc. And so Galileo considered him a friend.

And he certainly thought Galileo was his friend. So life suddenly changes when the Pope is somebody you've known for several years, and is thought to be a friend. So the assayer, which I'll talk about in just a moment, is actually dedicated to Urban VIII. I'm gonna keep calling him Barberini, and often Maffeo because his nephew is an important figure in this story too, another Cardinal.

Galileo starts making an effort to have the Copernican Decree revoked, pushing it with Urban. Well, with Barberini as much as possible. And he got the sense from Barberini, as a kind of testing of the water, got a sense from the Pope, things had really changed. He could start pushing Copernicanism more.

He tested that fairly strongly by writing a reply to a 1616 book by Engoli. I think that's the correct pronunciation. 1616 book that had argued against Copernicanism. Galileo defending it in the form of a letter that the Pope did not complain about. Okay, so with that, he decided he's now finally gonna write his System of the World, which had been hanging.

It takes him five years to write it, partly because of illness. There are moments during those five years, where he gets an audience with the Pope and reads parts of it to him out loud. And what appears to have been told to him by the Pope, this is all just fine as long as you recognize, and always recognize as hypothetical.

There's no convincing evidence of it yet. I'll go a step further. Barberini's own view, was that God was sufficiently powerful, that he could make it appear to us any way imaginable. And therefore, in principle, it was beyond our capacity to say what was really true. That was the Barberini position, and I'll show you why I stress that in a couple of moments.

Galileo, the dialogue gets completed in 1630. Now he's gotta have the stamp of approval, the imprimatur, and the nihil obstat from the Church. Nihil obstat, nothing stands out. The imprimatur is the imprimatur. And he doesn't get it right away. People are afraid. So it takes him the better part of two years to get the imprimatur, then to get permission to have it printed and published in Florence rather than Rome.

It comes out in February of 1632. Six months later, the church orders all books to be confiscated and all sales halted. I trust you all imagine how little effect that's going to do. It's going to make the book all the more desirable. And two months later, Galileo was summoned to Rome.

He actually asks the Duke, should he go? The Duke says yes, and puts him up in the Tuscan embassy in Rome. Now the sequence arrives in Rome, is allowed to stay at the Tuscan embassy, questioned twice by Father, and I'm not gonna go through the names. Notice the Cardinal Barberini, that is the Pope's nephew.

And it's fairly clear they want to deal leniently with Galileo. Galileo gives his defense. A report is put forward to the Pope, and I'm not gonna read through the rest of this because this chronology is coming from a book. We know a lot more now. What appears to have happened is that ten people who were responsible for the inquisition of Galileo.

By the way, he was shown torture, the items of torture, but never tortured or anything like that. He's in his mid-60s. He was shown a good deal of respect. In fact, he was nearly 70 at this time. Shown a good deal of respect, etc., by these people. And they apparently reached a deal with him that was going to be relatively lenient, not requiring him to do, well not putting him in house arrest for the rest of his life, in effect.

We don't have a document saying what happened then. So, the standard conclusion now is when the Pope saw this, he said absolutely not. This guy is going to house arrest for the rest of his life, period. And the best evidence we have for this, is when Galileo died, and they went to the Pope to ask to build a monument for him, categorically no.

There will be no monuments for Galileo. Now, I'll just quickly tell you why this would be, that the Pope would do this. This is a personal friend, right? The Pope's in a lot of trouble. The 30 years of war is at its height. All sorts of countries are demanding financial support to fight the Protestants, to rid the world of Protestant governments, thereby being able to enforce Catholicism.

Get rid of the Protestant governments, the rest takes care of itself, right? We're seeing that in the Mid East in the present moment. And he doesn't want to do this. He doesn't want to get embroiled in this. He doesn't really have the money. So he's in a very politically sensitive position, with lots of people criticizing him.

Now this book comes out, what's the point of the book? To in effect, throw the curriculum of the universities out the window. To throw scholasticism out the window, and replace it with an entirely new curriculum. That was his objective. The book is written in Italian. It's not written in Latin.

It is not for the scholarly community. It's for the everyday literate person in the street. Not all of whom could read Latin, but they could read Italian. But worst of all, we get to the end of the book, and what's the last section? It's Barberini's view of the matter, laid out very nicely in two and a half, three pages at the very end of the book.

Of course, God could be doing anything here. There's no way we could know, so there's no reason to fight about this, etc. We can entertain it. We can enjoy arguing about it, but we'll never know. He put those words in Simplicio's mouth, the fool's mouth. And I'm sure Urban VIII did not read the whole book, but I'm absolutely sure the people around him read that portion to him unmistakably.

Okay, and at that point he probably felt like a personal friend, long-standing personal friendship, had been profoundly violated, and wanted to throw the book at Galileo. And that appears to be precisely what happened. So you can see the rest. He's first sentenced to house arrest, and is allowed to go to the archbishop of Sienna.

Then allowed after a few weeks actually, to go to his own village just outside Florence. Over time he starts to lose his eyesight, so he moves into Florence. And it's during this period that his oldest daughter spends a lot of time supporting him and caring for him, Virginia.