Why was Galileo unable to defend himself?

Permanence

So after the papal admonition, he went ahead and published Dialogue on the two main world systems (1632). In the book he pretended to be bringing light to both sides of the argument, but essentially he was writing to say Ptolemy was wrong.

By numbers I meant proofs and anything logical in nature. He had brought up some major points, that were scientific in nature, while arguing for Copernicus. I'm not too familiar with the entire trial, but I was getting at the idea that he couldn't expect to go into that trial and say here is the logic and reasoning behind my notions, I'll be on my way.

NemoReally

No, he couldn't - Galileo wasn't the only one using logic and reasoning. There were a number of valid arguments against the Copernican model and both alternative explanations for some observations and lack of explanation for others in the Copernican model. Several of the people examining Galileo's arguments would likely have been as well versed as Galileo in logic and reasoning, but they would have been arguing from the POV that the Bible and the Ptolemaic system were valid (ie, they provided their axiomatic base) - it's fairly standard to assume the validity of the status quo and for arguments against it to carry the burden of proof.

It is worth bearing in mind that the Earth-centric, epicyclic model was capable of giving good agreement with observation and could, in principle, be refined to give more exact agreement.

BobG

This was the selling point. This was in the preface introducing the points that Galileo intended to discuss. In actuality, claiming this was intended as an insult to the Pope was pretty thin, but if enough people believed it was an insult, then the Pope had to act on it, whether he believed it to be an insult or not. The Pope had problems of his own and standing up for Galileo would have just made his own problems worse. In other words, the church really did do Galileo wrong.

Who knows what the motivation for persecuting him was. Different members of the church had different views on celestial mechanics - a Copernican model, a Ptolemaic model, and Tycho Brahe's model (that said the Sun and Moon orbited the Earth, while the planets orbited the Sun). There were legitimate arguments for and against each at the time, but the arguments tended to be as much personal attacks on people holding opposing view points as they were logical discussions.

In any event, the actual offense Galileo was found guilty of wasn't as important as finding him guilty of something, with his advocacy of the Copernican model being only one of his offenses.

Defending himself with physical evidence or logic really would have been inadequate for his era. He really needed his allies to mount more substantial personal attacks on his enemies and that involved risk. Personal attacks were not only decided by reputation, but winning these helped a person's reputation while losing these damaged a person's reputation. It wasn't an age dominated by science.

AnTiFreeze3

I'm glad someone mentioned this; Pope Urban VIII admired Galileo, and the two even had dinner semi-frequently. Galileo was given permission to write about the Copernican Theory, so long as he treated it as a hypothesis, and didn't try to make any bold claims. However, in Galileo's Dialogue Concerning the Two Chief Systems of the World, he included an argument promoted by a character named Simplicio (which can be translated to "simple minded"). The argument was one for the omnipotence of God, which Galileo then dismantled and more or less destroyed in the rest of his book.

This argument was personally introduced to Galileo by Pope Urban VIII himself. As you can probably tell, the Pope no longer felt too inclined to defend Galileo. Thus the persecution.

The lesson for today is that it all comes down to who you know, and how well you treat them

greswd

that sounds quite interesting.