QuestionsShould we believe without proof?Scripture teaches how to go to heaven, not how the heavens go
Should we believe without proof?Two separate domains

Scripture teaches how to go to heaven, not how the heavens go

The Letter to the Grand Duchess Christina

Galileo Galilei 1564 · 1642Astronomer and physicist: he holds that nature is read through experiment and mathematics, and that Scripture speaks of salvation, not of the mechanics of the heavens.
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What it claims

In questions of nature, a verse that seems to contradict a demonstrated fact does not prevail: it is its apparent sense that must be reconsidered. The Holy Spirit wants to teach us how one goes to heaven, not how the heavens go.

Why

Scripture cannot lie, but its true meaning is often hidden: against a demonstrated fact, it is the literal reading that gives way.

The same idea through history
Augustine of Hippo401Galileo leans on Saint Augustine (De Genesi ad litteram, book I, which Galileo's marginal note sends to chapters 18 and 19): an opinion about nature is against the faith only if it is refuted with absolute certainty, and the error then comes from human ignorance, not from Scripture.
Galileo Galilei1615The version presented here: a letter written in Italian, for a grand duchess, in the middle of the quarrel over Copernicus's system.
Stephen Jay Gould1997Gould takes up Galileo's formula in another form ("we study how the heavens go, and they determine how to go to heaven") to defend two domains that do not overlap.
In short

"Scripture teaches how to go to heaven, not how the heavens go" is an argument by Galileo Galilei (Letter to Christina of Lorraine, 1615, 1615) on the question "Should we believe without proof?" (answer: two separate domains). Its claim: In questions of nature, a verse that seems to contradict a demonstrated fact does not prevail: it is its apparent sense that must be reconsidered. The Holy Spirit wants to teach us how one goes to heaven, not how the heavens go. According to AskPhilosophy's logic check (Z3 solver), the conclusion does follow from its 4 premises. AskPhilosophy presents 2 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

Letter to Christina of Lorraine, 1615
Valid

In 1615, Galileo's opponents claim that the Bible says the Sun moves and the Earth stands still, and that saying the opposite is against the faith. Galileo answers in a long letter, which circulates in copies before being printed in 1636. He does not say the Bible is wrong. He says Scripture cannot lie, but those who read it can be mistaken, and that on questions of nature one must start from experience before quoting a verse.

P1Holy Scripture can never lie, provided its true meaning has been reached. That true meaning is often hidden and very different from the bare sense of the words.
P2For certain facts of nature, we have (or can have) certainty through sensory experience or necessary demonstrations. Such a fact must not be called into doubt, still less condemned, because of a verse whose words seem to say something else.
P3Two truths cannot contradict each other. If the manifest sense or demonstration has made us certain of a fact of nature, the true senses of the sacred texts can only agree with it.
P4The sacred writers spoke according to the capacity of a rough and uneducated people. When the literal sense of a passage about nature contradicts a demonstrated fact, it is therefore the literal sense that is not the true sense, and interpreters must look for the one that agrees with the fact.
Therefore, in questions of nature, a verse that seems to contradict a demonstrated fact does not prevail: it is its apparent sense that must be reconsidered. The Holy Spirit wants to teach us how one goes to heaven, not how the heavens go.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Valid, with no hidden premise. If Scripture is true (P1) and the fact of nature is really demonstrated (P2), they cannot contradict each other (P3). If the literal sense nonetheless seems to contradict the fact, then that literal sense is not the true one, and another sense must be sought (P4). The weight rests on P2: the argument is conditional. It does not say that the Earth's motion is demonstrated, it says what to do when a fact is. In 1615 and 1616 that is exactly what his opponents deny: for them, the Earth's motion is not demonstrated. The closing formula (how one goes to heaven) is one Galileo says he heard from a very high-ranking churchman; a marginal note in the letter names Cardinal Baronio.
Analogy. A mountain guide tells you: "the path climbs to the hut". If you measure and the path goes down, you do not conclude that the guide lies: you understand he was speaking of where you are headed, not of the profile of the ground. But you must first be sure of your measurement.

Objections

2

Each objection is a conversation: click to see who replies and where the debate stands.

C
Cardinal Bellarmine 1615 · attacks premise 2

Bellarmine accepts the principle, under a condition. If there were a true demonstration that the Sun is at the centre and the Earth moves, one would have to explain with great care the passages that seem contrary, and say that we do not understand them rather than say that what is demonstrated is false. But he will not believe there is such a demonstration until it is shown to him. And in case of doubt, one must not abandon Scripture as read by the Fathers.

Galilei replies
Galilei Galileo, in the same letter
Galileo writes that, if a conclusion cannot be declared heretical while one may doubt that it is true, the labour of those who want to condemn the Earth's motion will be in vain unless they first show it to be impossible and false.
The debate goes on (our summary) This passage shifts the burden of proof to his opponents, but it does not answer Bellarmine's request: to show a demonstration of the Earth's motion. Galileo had no decisive one in 1615; his argument from the tides, for instance, was not correct. The basic disagreement remains: who must prove, and what do we do while proof is missing? (Our summary.)
Where the debate stands (our summary)Both sides accept the principle (a true demonstration would force a reinterpretation of the text). They differ on a fact: did the demonstration exist in 1615? Bellarmine says no, Galileo judges the observations already sufficient.
T
The Holy Office 1633 · attacks premise 4

In the sentence of the 1633 trial, the Holy Office recalls that its theologians judged the proposition "the Sun is the centre of the world and immovable" absurd and false in philosophy, and formally heretical because it is expressly contrary to Scripture. The literal sense of the text thus prevails over Galileo's hypothesis.

a defender replies
We have not yet found a direct reply by Galilei in the texts.
J
John Paul II defender of the argument · 1992
Summary: before the Pontifical Academy of Sciences, John Paul II judges that most theologians of the time did not perceive the distinction between Holy Scripture and its interpretation. They thus transposed into the domain of faith a question of fact that belonged to scientific research.
G
George Coyne 2005
Summary: the Jesuit astronomer George Coyne doubts this diagnosis. In his view, the distinction between Scripture and its interpretation was known to the Holy Office consultors since Augustine. Their mistake was another: they required a demonstration of Copernicanism before giving up the literal sense.
Where the debate stands (our summary)The Church today acknowledges the 1633 error. The disagreement concerns its nature: ignorance of the distinction between text and interpretation (John Paul II), or too strong a demand for proof before reinterpreting (Coyne). In the second case, one finds again the question Bellarmine raised.