“As I’d like to show Galileo our world, I must show him something with a great deal of shame,” Richard Feynman famously wrote in lamenting the “actively, intensely unscientific” state of mainstream culture. But true and tragic as that might be to a degree, we owe much of the enormous scientific progress we’ve made in the past millennium to Galileo himself, father of modern science. It seems fitting, in light of the recent historic papal resignation, to revisit Galileo’s monumental impact on the rift between science and religion as he dethroned Earth from the center of the heavens with his discovery of heliocentrism, sparking the Scientific Revolution.

In 1615, as the Roman Inquisition was beginning to investigate his heretical heliocentric model of the universe, Galileo — who knew how to flatter his way to support — wrote to Christina of Lorraine, the Grand Duchess Christina of Tuscany. The lengthy letter, found in Discoveries and Opinions of Galileo (public library), explores the relationship between science and scripture. Galileo bemoans his critics who “remaining hostile not so much toward the things in question as toward their discoverer” and follows the three rules to refuting any argument that Susan Sontag would outline half a millennium later, making an eloquent case for why blind adherence to sacred texts shouldn’t be used to disarm the validity of scientific truth.

He begins:

To the Most Serene Grand Duchess Mother: Some years ago, as Your Serene Highness well knows, I discovered in the heavens many things that had not been seen before our own age. The novelty of these things, as well as some consequences which followed from them in contradiction to the physical notions commonly held among academic philosophers, stirred up against me no small number of professors-as if I had placed these things in the sky with my own hands in order to upset nature and overturn the sciences. They seemed to forget that the increase of known truths stimulates the investigation, establishment, and growth of the arts; not their diminution or destruction. Showing a greater fondness for their own opinions than for truth they sought to deny and disprove the new things which, if they had cared to look for themselves, their own senses would have demonstrated to them. To this end they hurled various charges and published numerous writings filled with vain arguments, and they made the grave mistake of sprinkling these with passages taken from places in the Bible which they had failed to understand properly, and which were ill-suited to their purposes. […] These men have resolved to fabricate a shield for their fallacies out of the mantle of pretended religion and the authority of the Bible. These they apply with little judgement to the refutation of arguments that they do not understand and have not even listened to.

Galileo laments a tendency of the human spirit to more easily rally around bullying than around celebrating, something we’ve seen compounded by the anonymity of the web today. He writes:

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.

Condemning the practice of taking biblical passages at face value without critical thinking and deeper semantic reflection — something that persists even today in matters of creationism vs. evolution and marriage equality — Galileo argues, as Neil deGrasse Tyson did five centuries later, that abandoning reason and evidence is a sign of both spiritual and intellectual laziness:

Now as to the false aspersions which they so unjustly seek to cast upon me, I have thought it necessary to justify myself in the eyes of all men, whose judgment in matters of religion and of reputation I must hold in great esteem. I shall therefore discourse of the particulars which these men produce to make this opinion detested and to have it condemned not merely as false but as heretical. To this end they make a shield of their hypocritical zeal for religion. They go about invoking the Bible, which they would have minister to their deceitful purposes. Contrary to the sense of the Bible and the intention of the holy Fathers, if I am not mistaken, they would extend such authorities until even in purely physical matters — where faith is not involved — they would have us altogether abandon reason and the evidence of our senses in favor of some biblical passage, though under the surface meaning of its words this passage may contain a different sense. […] Yet even in those propositions which are not matters of faith, this authority ought to be preferred over that of all human writings which are supported only by bare assertions or probable arguments, and not set forth in a demonstrative way. This I hold to be necessary and proper to the same extent that divine wisdom surpasses all human judgment and conjecture. But I do not feel obliged to believe that the same God who has endowed us with senses, reason and intellect has intended us to forego 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.

He stresses the importance of interpreters and sense-makers in extracting truth from scripture, admonishing against the tendency to form an opinion because it is popular and thus easy, rather than because it is wise:

People who are unable to understand perfectly both the Bible and the science far outnumber those who do understand them. The former, glancing superficially through the Bible, would arrogate to themselves the authority to decree upon every question of physics on the strength of some word which they have misunderstood, and which was employed by the sacred authors for some different purpose. And the smaller number of understanding men could not dam up the furious torrent of such people, who would gain the majority of followers simply because it is much more pleasant to gain a reputation for wisdom without effort or study than to consume oneself tirelessly in the most laborious disciplines.

Speaking to the same friction between “the Truth of the Universe” and “human truth” that Einstein and Tagore debated centuries later, Galileo points out that rather than an antidote to the divine, nature itself is a manifestation of divinity:

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. For that reason it appears that nothing physical which sense­experience sets before our eyes, or which necessary demonstrations prove to us, ought to be called in question (much less condemned) upon the testimony of biblical passages which may have some different meaning beneath their words. For the Bible is not chained in every expression to conditions as strict as those which govern all physical effects; nor is God any less excellently revealed in Nature’s actions than in the sacred statements of the Bible.

At the heart of Galileo’s argument is a reminder that it is ignorance that drives knowledge; he writes:

Hence I should think it would be the part of prudence not to permit anyone to usurp scriptural texts and force them in some way to maintain any physical conclusion to be true, when at some future time the senses and demonstrative or necessary reasons may show the contrary. Who indeed will set bounds to human ingenuity? Who will assert that everything in the universe capable of being perceived is already discovered and known? Let us rather confess quite truly that ‘Those truths which we know are very few in comparison with those which we do not know.’ […] Now if the Holy Spirit has purposely neglected to teach us propositions of this sort as irrelevant to the highest goal (that is, to our salvation), how can anyone affirm that it is obligatory to take sides on them, that one belief is required by faith, while the other side is erroneous? Can an opinion be heretical and yet have no concern with the salvation of souls? Can the Holy Ghost be asserted not to have intended teaching us something that does concern our salvation? I would say here something that was heard from an ecclesiastic of the most eminent degree: “That the intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes.”

Of those who tend to conflate opinion with fact, Galileo admonishes:

Let them freely admit that although they may argue that a position is false, it is not in their power to censure a position as erroneous.

Sharing in the spirit of Bertrand Russell’s famous words — “Do not fear to be eccentric in opinion, for every opinion now accepted was once eccentric.” — Galileo calls for standing by personal convictions even when they prove unpopular amongst the masses:

In my opinion no one … should close the road to free philosophizing about mundane and physical things, as if everything had already been discovered and revealed with certainty. Nor should it be considered rash not to be satisfied with those opinions which have become common. No one should be scorned in physical disputes for not holding to the opinions which happen to please other people best…

In the concluding paragraphs, Galileo admonishes against confirmation bias and the filter bubble of information that causes an echo chamber of opinion for those who would rather be self-righteous than fully understand:

Those who believe an argument to be false may much more easily find the fallacies in it than men who consider it to be true and conclusive. … The more the adherents of an opinion turn over their pages, examine the arguments, repeat the observations, and compare the experiences, the more they will be confirmed in that belief.

Complement this with Richard Feynman on the role of scientific culture in modern society.