Ryan Boissonneault Science & Nature

How Galileo Built the Wall of Separation Between Science and Religion

Between the years of 1609 and 1611, Galileo Galilei made more paradigm-shifting observations than perhaps any scientist in the history of the West. By pointing his telescope up at the sky, he had discovered the moons of Jupiter, the phases of Venus, the craters of the moon, sunspots, and stars at previously unfathomable distances. In doing so, he gave the world the evidence it needed to dethrone Aristotle and Ptolemy and crown Copernicus as the father of modern astronomy.

The Catholic Church, wholly unprepared for this avalanche of evidence, had to either admit its errors or condemn the science. It chose the latter. In 1633, Galileo was coerced, under the threat of torture, to publicly recant his views on heliocentrism—despite overwhelming evidence to the contrary—and forced to spend the remainder of his life under house arrest. Here was the official charge:

We say, pronounce, sentence, and declare that you, the said Galileo, by reason of the matters adduced in trial, and by you confessed as above, have rendered yourself in the judgment of this Holy Office vehemently suspected of heresy, namely, of having believed and held the doctrine—which is false and contrary to the sacred and divine Scriptures—that the Sun is the center of the world and does not move from east to west and that the Earth moves and is not the center of the world; and that an opinion may be held and defended as probably after it has been declared and defined to be contrary to the Holy Scripture.

On a strictly literal reading of the Bible, the Church was right. “[God] set the earth on its foundations; it can never be moved” (Psalm 104:5), declares one of several passages portraying the Earth as the immovable center of creation. Joshua himself stopped the Sun dead in its tracks for a full day (see Josh. 10:12–13). But this was precisely the problem. According to Galileo, interpreting scripture literally was a grave mistake. 

In Galileo’s Letter to the Grand Duchess Christina—one of the great manifestos of intellectual freedom in the West—he argued that nature must be read through observation and experiment, not through biblical commentary. And with that argument, Galileo began the long project of building a wall of separation between science and religion. Let’s explore the four foundations on which that wall was built.

1. God Did Not Grant Us Reason to Forgo Its Use

We can begin with Galileo’s defense of reason itself. “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,” Galileo declared. Galileo reasoned that, if we can’t trust our own senses and intellect, then that would implicate God in granting us defective faculties that perpetually mislead us. But if God is good—as theologians and philosophers alike insisted—then He would not deceive us in such a direct and systematic fashion. Ergo: If it looks like Venus revolves around the Sun, then that means that it probably does. 

For Galileo, the book of nature is written in the language of mathematics, and God is its author and chief mathematician. If we want a deeper understanding of our creator, then we had better start learning his language. As Galileo wrote:

It [the universe] is written in the language of mathematics, and the characters are triangles, circles, and other geometrical figures, without which it is humanly impossible to comprehend a single word of it, and without which one wanders in vain through a dark labyrinth.

While atheists may recoil at the suggestion that mathematics or science has anything to do with God, the larger point is that, even if God exists—and further that the Bible is in some way inspired—religion still has no place in the world of scientific inquiry. This is because salvation, even if you believe in it, does not depend on science, nor does science require its blessings. 

2. Biblical Literalism Leads Us Astray

If it’s true that God created the universe in the language of mathematics, and mathematics is entirely absent in holy scripture—as is any mention of physics, or chemistry, or the germ theory of disease—then how could a scientific understanding of the world be necessary for salvation? As Galileo wrote:

Now if the Holy Spirit has purposely neglected to teach us [scientific] 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?

The Bible, Galileo maintained, is not a science textbook, and to regard it as such is to perpetually “fall into error.” “The intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes,” Galileo wrote. In other words, Biblical literalism is a farce. When addressing physical problems, “we ought to begin not from the authority of scriptural passages but from sense experiences and necessary demonstrations,” Galileo concluded. 

The Bible is no more a guide to physical reality than is The Lord of the Rings. We may derive moral instruction from them, but taking them literally leads to a corruption of our sanity. 

3. The Bible Is a Vehicle for Moral Guidance

Scripture, on a Galilean reading, is an instrument for moral truth and spiritual growth (although we’ll argue elsewhere that it shouldn’t even be used for that), but its authors took the necessary creative liberties to convey these moral lessons in easily accessible narratives for ordinary people. Yet if you take these narratives literally, they become, in the starkest of terms, idiotic. 

The passages of the Bible that “assign to God feet, hands and eyes, as well as corporeal and human affections,” wrote Galileo, “were set down in that manner by the sacred scribes in order to accommodate them to the capacities of the common people, who are rude and unlearned.” Translation: the Bible spins higher spiritual and moral truths into simple tales for simple people. Had the Bible been written by philosophers, it would be about as widely read among ordinary people as Aristotle’s Nicomachean Ethics. 

The great mistake of orthodox religion is the reading of allegory as literal truth. And the great sin of the Catholic Church, for Galileo, was the institutional propagation of this grievous interpretive error. Only by recognizing this error—and cleaving scripture from science permanently—could humans hope to make any progress at all. 

4. The Wall of Separation Prevents the Illusion of knowledge

In a letter to the Danbury Baptists, Thomas Jefferson once wrote of “building a wall of separation between Church & State.” By this, Jefferson meant that an individual’s religious beliefs were a personal matter, holding no influence in the public sphere beyond motivating actions that can be defended in religiously neutral terms. Likewise, the government had no authority to dictate the contents of one’s conscience. 

Galileo never used Jefferson’s famous phrase, but the principle was remarkably similar. Like Jefferson, he thought that religious beliefs were deeply personal, but that religion had no more place in the realm of science than it did in politics. And as with politics, the mixing of religion with science leads only to confusion, error, coercion, and violence (as he would well know). 

When the Bible is misinterpreted as a literal text—forming the basis for scientific views—it has the additional, unwelcome effect of furnishing otherwise uninformed individuals with the illusion of actual knowledge. As Galileo explained:

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.

In fact, nature is not understandable to most men, because it’s written in the difficult language of mathematics. True scientific knowledge is therefore hard-won—the result of years of intense study—while the illusion of knowledge is easily attained—the result of listening, for instance, to a sermon or two. But this creates a class of individuals doubly ignorant—both of science and of the original intention of the Bible. As Galileo wrote:

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.

The temptation for superficial knowledge is, in other words, always present. Why spend decades of your life learning the intricacies of astrophysics when you can read Genesis in an afternoon and become an expert in both cosmology and salvation in one sitting? Charlatans of every type—eager to exploit this tendency—readily gain followers by stroking their egos and promising expertise with minimal effort or study. But this is not education; it’s delusion. As the American historian Daniel J. Boorstin put it, “The greatest obstacle to discovery is not ignorance, it is the illusion of knowledge.”

The illusion of knowledge goes by many names today: creation science, intelligent design, biblical archaeology, faith-based cosmology. The labels change, yet the underlying temptation does not. Four centuries after Galileo, countless people still prefer certainty to inquiry, authority to evidence, and revelation to investigation.

Galileo understood what was at stake. The conflict was never only about whether the Earth moves around the Sun. It was about a deeper question: when observation and scripture collide, which one yields? Modern science was born the moment Galileo gave his answer, and built his impenetrable wall.

References & Further Reading