Letter to the Grand Duchess Christina

“They know that it is human nature to take up causes whereby a man may oppress his neighbor, no matter how unjustly, rather than those from which a man may receive some just encouragement.”

Galileo asserts that he knows how human nature works, at least in this particular way, and that all people tend to try to oppress those around them. He does this to explain how his detractors have gained support—it is not because they are right but because people enjoy attacking others.

“I hope to show that I proceed with much greater piety than they do, when I argue not against condemning this book, but against condemning it in the way they suggest—that is, without understanding it, weighing it, or so much as reading it.”

Galileo garners sympathy by making it clear that he has criticisms of Copernicus’s book, even though they may not be the same criticisms his detractors have—or, for that matter, the same criticisms that Duchess Christina has. He still engenders sympathy between himself and his readers, even if they disagree with him.

“The reason produced for condemning the opinion that the earth moves and the sun stands still is that in many places in the Bible one may read that the sun moves and the earth stands still. Since the Bible cannot err, it follows as a necessary consequence that anyone takes an erroneous and heretical position who maintains that the sun is inherently motionless and the earth movable.”

Galileo uses the passive voice to explain an opinion that he doesn’t hold. Here, he explains why people think heliocentrism is heretical, and he sets up his discussion comparing literal readings of the Bible to metaphorical readings.

“It is necessary for the Bible, in order to be accommodated to the understanding of every man, to speak many things which appear to differ from the absolute truth so far as the bare meaning of the words is concerned. But Nature, on the other hand, is inexorable and immutable; she never transgresses the laws imposed upon her, or cares a whit whether her abstruse reasons and methods of operation are understandable to men.”

Galileo uses personification to express the difference between the natural world and the Bible. He gives “Nature” feminine pronouns and a personality, which makes “her” both endearing and also easier to pin down. His version of nature is mysterious and unchanging, and does not need to communicate with people; the Bible, however, does need to communicate with people.

“But I do not feel obliged to believe that that same God who has endowed us with senses, reason, and intellect has intended to forgo their use and by some other means to give us knowledge which we can attain by them. He would not require us to deny sense and reason in physical matters which are set before our eyes and minds by direct experience or necessary demonstrations. This must be especially true in those sciences of which but the faintest trace (and that consisting of conclusions) is to be found in the Bible.”

Galileo infers that because God gave us senses, reason, and intellect, it is not sacrilegious to use them to understand the universe. He intends to discuss things that the Bible seems to contradict, even though it mentions those things only briefly.

“They say that since theology is queen of all the sciences, she need not bend in any way to accommodate herself to the teachings of less worthy sciences which are subordinate to her; these others must rather be referred to her as to their supreme empress, changing and altering their conclusions according to her statutes and decrees.”

Galileo uses an extended metaphor of a “queen” or an “empress” to describe the study of theology. He extends it (i.e., uses it more than once, and in different ways) both because it’s a metaphor his detractors have used and because there are multiple aspects of it that he wants to dismantle. 

“I may deduce this doctrine: In the books of the sages of this world there are contained some physical truths which are soundly demonstrated, and others that are merely stated; as to the former, it is the office of wise divines to show that they do not contradict the holy Scriptures. And as to the propositions which are stated but not rigorously demonstrated, anything contrary to the Bible involved by them must be held undoubtedly false and should be proved so by every possible means.”

Galileo claims that the theologian’s job is to make the Bible fit facts about the physical world, not the other way around. He also claims that theologians shouldn’t believe any statement about the physical world that nobody has yet proved to be true. He uses the passive voice to indicate a broad category and avoid insulting anyone in particular.

“And Your Highness, knows what happened to the late mathematician of the University of Pisa who undertook in his old age to look into the Copernican doctrine in the hope of shaking its foundations and refuting it, since he considered it false only because he had never studied it. As it fell out, no sooner had he understood its grounds, procedures, and demonstrations than he found himself persuaded, and from an opponent he became a very staunch defender of it.”

Galileo gives an example of what his detractors should do. Rather than criticizing him for holding a theory they do not understand, they should study the theory. If they would, they might have the same experience as this mathematician. They could be persuaded by reason rather than remaining stuck in their prejudices.

“It would be necessary to forbid men to look at the heavens, in order that they might not see Mars and Venus sometimes quite near the earth and sometimes very distant, the variation being so great that Venus is forty times and Mars sixty times as large at one time as another. And it would be necessary to prevent Venus being seen round at one time and forked at another, with very thin horns; as well as many other sensory observations which can never be reconciled with the Ptolemaic system in any way, but are very strong arguments for the Copernican.”

Galileo describes the physical observations that he says would be “necessary to omit” to maintain a belief in the Ptolemaic system. He makes sure that nothing he says is omitted since he writes it down here. To believe the Ptolemaic system is true requires us to disbelieve the testimony of our senses.

“If the Bible, accommodating itself to the capacity of the common people, has on one occasion expressed a proposition in words of different sense from the essence of that proposition, then why might it not have done the same, and for the same reason, whenever the same thing happened to be spoken of?”

This rhetorical question is not meant to be answered by the reader (Galileo follows it with an answer). Instead, it is meant to make the reader think and to help the reader agree with Galileo’s argument.

“Copernicus himself knew the power over our ideas that is exerted by custom and by our inveterate way of conceiving things since infancy. Hence, in order not to increase for us the confusion and difficulty of abstraction, after he had first demonstrated that the motions which appear to us to belong to the sun or to the firmament are really not there but in the earth, he went on calling them motions of the sun and of the heavens when he later constructed his tables to apply them to use.”

Galileo uses Copernicus as a respected example. He argues that because Copernicus simplified his explanations to make them accessible to people, simplifying explanations to the point of inaccuracy is sometimes reasonable and necessary.

“I think this may be an arbitrary simplification of various council decrees by certain people to favor their own opinion.”

Galileo uses understatement to protect himself from offending his readers. By using words like “may” and “certain people,” he softens his accusation. He uses irony here, as well; he means to say, “of course that’s what these people are doing.”

“Anyone can see that dignity is most desired and best secured by those who submit themselves absolutely to the holy Church and do not demand that one opinion or another be prohibited, but merely ask the right to propose things for consideration which may the better guarantee the soundest decision…”

Galileo again refers to a general audience, or a sort of general principle of humanity. Anybody, no matter who they are (and this includes the reader), will agree with Galileo’s argument.