July 1

An Open Mind: Lessons from the Galileo Affair

Having an open mind or getting someone else to open up their mind to a different point of view is hard work. But it can be done. The Galileo affair from the 17th century has some classic lessons and some do's, but mostly don'ts, on how to get someone to change their perspective, especially when the change in question is a radical one.

Galileo's Trial

The year was 1633. Galileo stood on trial in front of the Inquisition (a powerful office within the Roman Catholic church), charged with "vehement suspicion of heresy."

Galileo's crime? He had published a book proposing that the sun, not the earth, was at the center of the universe. If confirmed guilty, his punishment would be severe. Mathematician Giordano Bruno was burned at the stake for espousing similar views not long before Galileo's trial.

The volte-face

To avoid the fate that had befallen his predecessor and the realization that his audience didn't and probably was never going to have an open mind, Galileo's survival instinct kicked in. He swallowed his pride and pretended he had been only hypothesizing and that his opinions were false. At his trial, he acknowledged

I must altogether abandon the false opinion that the sun is the center of the world and immovable, and that the earth is not the center of the world, and moves.

Galileo went on to say,

with sincere heart and unfeigned faith I abjure, curse, and detest the aforesaid errors and heresies, and generally every other error, heresy, and sect whatsoever contrary to the said Holy Church, and I swear that in the future I will never again say or assert, verbally or in writing, anything that might furnish occasion for a similar suspicion regarding me.

Upon hearing the 180-degree-turn from Galileo, the Inquisition agreed to lighten his sentence.

Galileo, already 69 at the time of the trial, spent the rest of his life under an indefinite house arrest ordered by Pope Urban VIII. Additionally, he had to seek repentance for his heretical thoughts by reciting the seven penitential psalms weekly for a few years. He died a sad man nine years later.


In his book, Great feuds in science: Ten of the liveliest disputes ever, Hellman describes how Galileo, a devout Catholic himself and a father of two daughters who became nuns, had never intended to go against the church. On the contrary, when he found sufficient evidence for the heliocentric theory (helio —the Greek root for sun—at the center), he merely sought to protect the church from having to defend itself in the face of mounting evidence.

So, why did the authorities respond so intensely to Galileo's suggested philosophy? What was the big deal about a physics theory almost costing Galileo his life?

To answer, let's rewind the story a little bit with the help of author Hal Hellman.

It all began with Ptolemy.

Ptolemy and Copernicus

Ptolemy, born in 100 AD, believed that the earth rested at the center of the universe and that other celestial objects such as the sun, moon, Venus, and Mercury circled the earth. The earth-at-the-center theory meshed with what people observed with their naked eyes—the sun and moon seemingly moving around us in the sky.

Moreover, Ptolemy's theory correlated nicely with the religious ideology that the earth is the only place for imperfect beings such as us mortals and that perfect eternal heaven in the form of other celestial objects is all around us. We simply have to find a way to get past the temptations, corruptions, and tragedies that bog our earthly lives to reach those celestial bodies.

Ptolemy's theories were steadfast for centuries until Polish astronomer and mathematician Copernicus proposed an alternative.

Based on his observations and findings, Copernicus advocated a new theory: that the sun, not the earth, is at the center of the universe. And that celestial bodies rotate around the sun, not because angels make them do it, but because it is their nature.

Looking for evidence

Galileo was convinced of the Copernican model of the universe but realized he'd need to produce evidence to justify such a radical theory. Serendipitously for him, a Dutch eyeglass maker Lipperhey had just then invented a device that could help magnify objects to three times their size—what subsequently became the modern telescope.

Galileo, who'd heard about the "Dutch perspective glasses," built his own telescope that could magnify images twenty-fold. Then he pointed his magnifying device skyward. The rest, as they say, is history.

Galileo saw craters on the earth's moon and dust-like planetary rings—evidence that went against the prevalent views of perfect heavenly bodies. More importantly, he saw enough evidence to convince him that the sun, not the earth, was at the center of the universe. This meant he had the unenviable job of reconciling his telescopic observations with the somewhat contrary language portrayed in the scriptures.

And so, Galileo decided to write the book Dialogue on the Great World Systems, Ptolemaic and Copernican, not foreseeing that it would eventually land him in front of the Inquisition.

Dialogue — the book

Had Galileo's book, Dialogue, been a dry piece of technical writing, or in the more uncommon language, Latin, it may not have ruffled as many feathers. But the book was lively, entertaining, readable, and encouraged discussion. Also, it was written in Italian—a more widely accessible language.

Galileo wrote Dialogue as a series of conversations between three characters:

Salviatti, representing Galileo himself

Sagredo, a neutral moderator

Simplicio, the opponent, represents the prevalent mindset, a composite of opposing views

Throughout the book, Salviatti builds the case for why the earth, and not the sun, is the planetary body in motion. One key argument is that the movement of water on earth—a phenomenon everyone could see and, therefore, agree with—is caused by earth's motion (though this was disproven later. Tides that move water are caused not by earth's movement, but instead by gravitational forces from the moon).

On the other hand, Simplicio's counter-argument in the book seems weak. He accuses Salviatti of speculation and trying to interpret Divine wisdom. He declares that if God wanted water to move, He could have done it in many ways, not necessarily just by making the earth rotate around the sun.

Galileo's misplaced optimism

Galileo believed he could convince the church of the heliocentric theory through Dialogue without reproach because he had, at least in his mind, a cordial and intellectual relationship with the church's leader, Pope Urban VIII.

Galileo, in his early days, was a student at the University of Pisa. There, he struck a friendship with Maffeo Vincenzo Barberini, a fellow student who later became Cardinal Barberini and eventually the Pope of the Roman Catholic church (assumed name Urban VIII).

Where Galileo went wrong

After assuming the papacy, however, the Pope grew skeptical of Galileo's theories, realizing how the theory would upend established church doctrines and contradict revered scriptures.

But even more critically, Galileo forgot that Simplicio's arguments in the Dialogue were actual papal arguments. So, it almost seemed like Galileo took pot shots at the Pope, the church, and its doctrines through his book. Of course, Pope Urban VIII found this personally downright insulting.

And that's how a supposed friend turned into a foe. The result? Galileo was hauled in 1633 before the Roman Inquisition, where he was forced to eat his own words.

It wasn't until two centuries later that the church allowed heliocentrism to be taught.

This entire episode, popularly referred to as Galileo's affair, has been a case study for how to (and how not to) introduce ideas that radically change the status quo. And even if the ideas aren't groundbreaking, here are some takeaways from the Galileo affair on how to have an open mind.

How to have an open mind

While Galileo's affair is a fascinating read, it has some important lessons for us on having an open mind when new ideas are concerned. These lessons are especially relevant today in a world where we are all stuck in our own bubbles and echo chambers.

What's in your Index Librorum Prohibitorum?

No, I'm not making up high-sounding words. Until it was formally abolished in 1966, a section of the Catholic Church maintained a list of books/writings Catholics were forbidden to read. This was referred to as the Index Librorum Prohibitorum—literally meaning the "list of prohibited books."

Books deemed antithetical to the church's cultural, political, and theological views were censored and made the list.

Not surprisingly, the list of banned authors features some of the brightest and most curious minds of our times from wide-ranging fields such as literature, philosophy, and science—Descartes, Voltaire, Pascal, Kant, Milton, and of course, Darwin. Their crime? They thought differently.

The truth is that each of us has our own index, not just of prohibited books but ideas, thoughts, and people we refuse to engage with because they are so "out there." But why are we put off by what we consider other?

Is it insecurity? Do the ideas threaten our beliefs and values?

Acknowledging and discovering why we avoid what we avoid is the first step to developing an open mind.

Understand the three stages of truth

All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident. German philosopher, Arthur Schopenhauer. 

When Galileo, and Copernicus before him, proposed heliocentrism, they were initially ridiculed because the theory went against the very grain of accepted wisdom at the time. People simply laughed it off.

But when Galileo started collecting evidence to prove his assertions, the reaction was swift—wild opposition for fear of disrupting the status quo. It only took two hundred years for the tide to turn and for heliocentrism to be adopted as the norm.

Keeping an open mind means being open to the possibility of change in our opinions, perceptions, and beliefs. And it is often hard to adapt to change.

Knowing and accepting the possibility that, like the five stages of denial, any new truths will take their time to go from ridicule to acceptance is the only way to be at peace through the change process.

Make it impersonal

Pope Urban VIII felt so insulted for being portrayed as Simplicio in Galileo's Dialogue that he never forgave Galileo.

Upon Galileo's death in 1642, his patron, the grand duke of Tuscany, wanted to hold a fitting public funeral and erect a monument to commemorate Galileo's contribution to humanity. But the Pope was vehemently opposed to this idea. So, the remains of one of the greatest scientific minds lay hidden in the church bell tower basement for over a century until they were finally moved to be near the tombs of other Florentine greats—Michelangelo and Machiavelli.

The lesson is this: if you'd like someone to have an open mind about an idea, it would help immensely not to insult them personally. We humans aren't rational beings and will always find it hard to separate ideas from people.

Evaluate the quality of your information

While this isn't directly tied to the Galileo affair, it's nevertheless a vital attribute to keeping an open mind.

Keeping an open mind is essential, but being able to separate fact from fiction is even more so.

If you don't read the newspaper, you are uninformed. If you read the newspaper, you are misinformed. Mark Twain

What Twain said was tongue-in-cheek, but it is indeed better to be uninformed than misinformed.

Being uninformed simply means you are not exposed to new information, but you still have the capacity to learn. On the contrary, when you are misinformed, you have already bought into some ideas. It is much more complicated than keeping an open mind and changing tracks, especially if it involves admitting you were gullible to believe the wrong idea in the first place.


Keeping an open mind means learning to break a mold you may have carefully constructed all your life. It can be jarring and may even result in an existential crisis.

But the truth, as they say, will set you free, even if it takes a little while. Or two hundred years, as in Galileo's case.



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