Faith and Science in Catholic Tradition: From the Early Church to Pope St. John Paul II

Above:  Painting of St. Augustine by Philippe de Champaigne (ca 1645)


Catholic tradition has much to say about the relation of science and faith.  In this article I will trace the development of that body of thought from its roots in Sacred Scripture to the teaching of Pope St. John Paul II.

A good place to start is with the Book of Genesis.  Many people today see that book as an example of primitive mythmaking, which invented false supernatural explanations of things for which we now have the true natural explanations, thanks to science.  But this is to read Genesis in an anachronistic way. The first chapters of Genesis were an attack on false supernaturalism, not a defense of it.

To take an obvious example, when Genesis said that the Sun and Moon were lights placed by God in the heavens to light the day and night, it was not proposing an alternative to modern scientific explanations of how the Sun and Moon formed. It was, rather, opposing the pagan religions of antiquity in which the Sun and Moon were worshipped as gods.  And when Genesis said that man is made in the image of God and is to exercise dominion over created things, it was opposing the pagan idolatry in which human beings worshipped created things or gods made in the image of created things.

In the pagan religions of Egypt, Babylon, Greece and Rome, the world was filled with supernatural forces, and populated by numerous deities — gods and goddess of the oceans and forests, of wind and fire and lightening, of sex and fertility, and so on.  But the Old Testament taught that there is only one God, who is not a part of the universe, or located within its space and time or within its phenomena and forces, but a God who is beyond the universe, a God who is indeed the Author of the universe.  In this way, biblical religion stripped the physical universe of divinity and supernatural elements and made it into a natural world, no longer the abode of gods, but merely the creation of the one God.  Old Testament revelation did not mythologize the physical universe but contributed to demythologizing it.

The very idea of a natural world, therefore, owes much to biblical religion.  It also owes a great deal, of course, to the philosophers and scientists of ancient Greece.  But whereas biblical religion saw Nature in relation to an ultimate source or Author, the Greek thinkers were primarily interested in Nature itself, on its own terms, and had no concept of a Creator.  So there was a clash of perspectives that in some ways foreshadowed the arguments of our own day.  This can be seen in one of the last books of the Old Testament, the Book of Wisdom, written around 50 BC by a Jewish writer in Alexandria, Egypt.  One passage of that book actually discusses the philosopher-scientists of ancient Greece and severely criticizes them for being blind to the Creator.  The passage reads as follows:

For all people who were ignorant of God were foolish by nature, and they were unable from the good things that are seen to know the one who exists, nor did they recognize the artisan while paying heed to his works;

but they supposed that either fire or wind or swift air or the circle of the stars or turbulent water or the lights of heaven were the gods that rule the world.

If through delight in the beauty of these things people assumed them to be gods, let them know how much better than these is their Lord, for the Author of beauty created them.

And if people were amazed at their power and working, let them perceive from them how much more powerful is the one who formed them.

For from the greatness and beauty of created things comes a corresponding perception of their Creator. 

Yet these people are little to be blamed, for perhaps they go astray while seeking God and desiring to find him.

For while they live among his works, they keep searching and trust in what they see because the things that are seen are beautiful.

Yet again, not even they are to be excused,

for if they had the power to know so much that they could investigate the world, how did they not more quickly find the Lord of these things?  (Wis 13:1-9)

Note the sympathy and even respect that the scriptural author showed toward those pagan scientists, because they “kept searching” and their search for truth was perhaps, at least unconsciously, a search for God.  But they were unable to see or think beyond Nature, and so made Nature, with its power and beauty, into the highest reality, putting it in the place of God.

The teaching of the Old Testament about the physical universe, then, is that it is neither inhabited by gods nor itself divine, but that it does point to God.  As the Book of Wisdom put it “from the greatness and beauty of created things comes a corresponding perception of their Creator.”  St. Paul famously echoed this in Romans 1:20, where he said that God, although invisible, can be known through the things he has made.  This is another very important point that people often misunderstand.  In Christian tradition, the primary evidence for the existence of God is not the supernatural, but the natural — for example, the fire, wind, swift air, circle of the stars, and so on, mentioned in the Book of Wisdom.

How does the natural world point its Creator?  From earliest times, Christian writers emphasized two ways. First, the fact that the world exists at all points to a giver of being, a causa essendi.  Second, the fact that the world is orderly, harmonious and beautiful points to a giver of order.  As St. Irenaeus wrote,  around 200 AD, “There exists but one God … He is the Father, God, the Creator, the Author, the giver of order.” 1 Or as St. Athanasius wrote in the fourth century, with Romans 1:20 clearly in the background, “God, by his own Word, gave to creation such order as is found therein, so that though he is by nature invisible, men might be able to know him through his works.” 2 Many early Christian wrote in the same vein.3

Not only is the world orderly, but its order is based on law.  Scripture itself speaks of God as Lawgiver, not only to the people of Israel and to mankind, but to the cosmos itself.  In Jeremiah 33:25, God declares,

“When I have no covenant with day and night, and have given no laws to heaven and earth, then too will I reject the descendants of Jacob and of my servant David.”

The very idea that there are laws of physics is rooted in Christian belief.  It originated with Descartes and Newton, both of whom saw these laws as having been imposed upon the world of matter by its Creator.4

Another theme found in many early Christian writers is that God is the “Author” of the world.  Indeed, many of the Church Fathers said that God is the Author of two books: the Book of Sacred Scripture and the Book of Nature or book of the universe.  For example, St. Augustine wrote,

“It is the divine page that you must listen to; it is the book of the universe that you must observe. The pages of Scripture can only be read by those who know how to read and write, while everyone, even the illiterate, can read the book of the universe.” 5

Now, it is obvious that if these two books have the same divine Author they cannot contradict each other.  If on some point they seem to disagree, we must be reading one or both of the books incorrectly.  St. Augustine warned against interpreting Scripture in a way that contradicts what is known about Nature by reason and experience. He wrote,

“Often a non-Christian knows something about the earth, the heavens, and the other parts of the world, about the motions and orbits of the stars and even their size and relative positions, about the predictable eclipses of the sun and moon, the cycles of the years and seasons, about the kinds of animals, shrubs, stones, and so forth, and this knowledge he holds with certainty from reason and experience. Now it is a disgraceful and dangerous thing for an unbeliever to hear a Christian, presumably giving the meaning of Holy Scripture, talking nonsense on these topics, and we should take all means to prevent such an embarrassing situation, … Reckless and incompetent expounders of Holy Scripture bring untold trouble and sorrow on their wiser brethren, … to defend their utterly foolish and obviously untrue statements, they will try to call on Holy Scripture, .. although they understand neither what they say nor the things about which they make assertion.” 6  [Emphasis added.]

The principle that Scripture should not be interpreted in a way that contradicts what is known with certainty by reason became axiomatic to theologians.  It was appealed to by Galileo and accepted also by Galileo’s opponents, including Cardinal Robert Bellarmine, who famously wrote in 1615 that

“if there were a real proof that … the Sun does not go round the Earth but the Earth round the Sun, then we should have to proceed with great circumspection in explaining passages of Scripture which appear to teach the contrary, and rather admit that we do not understand them than declare an opinion to be false which has proved to be true.” 7

From the fact that the universe is a book written by God, another conclusion was drawn by theologians, which is that the universe has its own unity and integrity and internal logic, just as a book written by a human author does. Within the plot of a novel, one thing causes another, even though all the things and events in the novel can also be fully attributed to the novelist.  In an analogous way, within the plot of the physical universe, one thing causes another, while at the same time all the things and events in the physical universe can be fully attributed to God as the Author of the universe.  This is the classic distinction in Catholic theology between the Primary Cause, who is God, and natural “secondary causes” within the created world.8

The traditional Catholic understanding is that while God can and in special cases does produce effects directly in a miraculous way, he ordinarily acts through natural secondary causes.  As the theologian Francisco Suarez, who died about four hundred years ago, put it, “God does not interfere directly with the natural order where secondary causes are sufficient to produce the intended effect.” 9

This principle was important for the founding of science, for it implied that when we see some strange event or new phenomenon we should look first for natural explanations and not assume a miracle — a point strongly emphasized by medieval theologians, philosophers and scientists, such as Nicolas Oresme and Jean Buridan.10  Buridan, for example, wrote,

“The philosophers explain [such marvels] by appropriate natural causes; but common folk, not knowing of causes, believe these phenomena are produced by a miracle of God, which is usually not true.” 11

We have seen that many elements of Jewish and Christian belief fit very well with the scientific outlook.  The world is the product of divine Reason and therefore made according to principles and laws that can be discovered and understood by reason.  And because the Creator is good, the world must be good and worth studying.

It is not surprising, then, that the Scientific Revolution of the 16th and 17th centuries took place within a civilization shaped by Christian belief.  And the great figures of that Revolution were virtually all devout Christian believers — Copernicus, Brahe, Kepler, Galileo, Descartes, Pascal, Boyle, Steno, Mersenne, Fermat, Grimaldi, Cassini, Newton, Leibniz, and the rest.  Most of the great scientists down to the time of Faraday and Maxwell in the mid-19th century continued to be believers.12

Now, all of this does not mean that there cannot be tension and even apparent conflicts between science and faith.  Of course, there can be and have been.  This is not surprising.  There have also always been tensions and conflicts within science and within theology.  Though truth cannot contradict truth, human progress in understanding truth is often slow and painful. The path of science is often a winding one, where science seems to be going in a certain direction and then suddenly and unexpectedly changes direction.

This is what happened in the Galileo affair.  Theologians and the magisterium of the Catholic Church had grown quite comfortable — too comfortable — with the astronomy of the ancient pagan Greeks, Aristotle and Ptolemy, which had been the scientific orthodoxy for 15 centuries; and theologians were therefore intellectually unprepared to deal with the Scientific Revolution that Copernicus and Galileo started.  The Galileo affair was enormously complex.  However, there is no escaping the fact that Church authorities acted rashly, with disastrous consequences.  That tragic affair had one positive result, however, which was that Church authorities in later centuries became much more circumspect in dealing with scientific developments.

For example, in the 18th and early 19th centuries, as science uncovered evidence that the Earth is much older than the chronologies in Genesis suggested, the magisterium remained relatively quiet.  Similarly, although Darwin published his Origin of Species in 1859, there was no papal pronouncement on evolution until 1950, almost a century later, despite the fact that evolution raised far more profound theological questions than Copernicanism did — questions about the origin and nature of man himself.

In 1893, when Pope Leo XIII felt it necessary to warn against the radical conclusions that some modern biblical scholars were reaching, especially in Germany, he issued the encyclical letter Providentissimus Deus.  While the pope was not afraid to confront the biblical scholars, he was quite deferential toward natural  science.  He wrote,

“There can never, indeed, be any real discrepancy between the theologian and the physicist, as long as each confines himself within his own lines, and both are careful, as St. Augustine warns us, ‘not to make rash assertions, or to assert as known what is not known.’” 13

Note that he says that both the scientist and the theologian must avoid such rashness.  We can see here an implicit acknowledgement of the mistakes theologians made in dealing with Galileo.  He went on to say,

“[W]e must remember, first, that the sacred writers, or to speak more accurately the Holy Spirit who spoke by them, did not intend to teach men these things (that is to say, the essential nature of the things of the visible universe), … . Hence they did not seek to penetrate the secrets of nature, but rather described and dealt with things in more or less figurative language, or in terms which were commonly used at the time, … .”

The idea that the simplistic descriptions of natural phenomena appearing in many passages of Scripture were an accommodation to the way people thought and spoke at the time the passages were written goes back to mediaeval and early Christian commentators on Scripture, who were well aware that some of those descriptions could not be taken literally.

The caution and patience of the magisterium with regard to science in the three centuries after the Galileo affair were wise and necessary.  Time was needed for science to travel along its winding path, to give it time to correct its own errors and reach more mature and reliable conclusions.  Time was also needed for theologians and philosophers to digest the discoveries of science and reflect upon the many subtle issues they raised.

But at some point, more than mere patience and restraint was required.  The magisterium needed to say something of a more positive nature to help the faithful navigate those theological and philosophical issues.

Two important steps were taken in this regard by Pope Pius XII.  In 1950, in his encyclical letter Humani generis, he addressed the evolution of human beings and gave a green light to acceptance of it if that is where the evidence led.  But he also drew an important line.  While at the physical level human beings may have evolved from non-human ancestors, he said, the human spiritual soul transcends matter and therefore cannot be the product of any merely material process.

Pope Pius XII took another important step. In 1951, in a famous address to the Pontifical Academy of Sciences,14 he warmly embraced the recent discoveries in astrophysics, geology, and other fields that pointed to the universe having a beginning several billion years ago.  In fact, Fr. Georges Lemaître, the Catholic priest and theoretical physicist who proposed the Big Bang Theory,15 was worried that that the pope was embracing it too warmly.

The next notable statement on science by the magisterium was made by the Second Vatican Council, which strongly affirmed the proper autonomy of science in its own sphere. In Gaudium et Spes we read,

“Therefore, if methodical investigation within every branch of learning is carried out in a genuinely scientific manner and in accord with moral norms, it never truly conflicts with faith, for earthly matters and the concerns of faith derive from the same God. Indeed, whoever labors to penetrate the secrets of reality with a humble and steady mind, even though he is unaware of the fact, is nevertheless being led by the hand of God, who holds all things in existence, and gives them their identity. Consequently, we cannot but deplore certain habits of mind, which are sometimes found too among Christians, which do not sufficiently attend to the rightful independence of science and which, from the arguments and controversies they spark, lead many minds to conclude that faith and science are mutually opposed.” 16

I think we can all recognize in the last sentence an implicit criticism of the Church officials who condemned Galileo as well as of the fundamentalist Christians who attack evolutionary biology on spurious theological grounds.

I come now finally to the writings and speeches of Pope St. John Paul II, which contain so much of value on the relation of science and faith that I will pick just one point to highlight, though it is a point of surpassing importance.

We saw that Pope Leo XIII in 1893 warned both the theologian and the scientist to stay within “his own lines” (or lanes, as we might say today) and “not to make rash assertions, or to assert as known what is not known.”  In the Galileo case one saw theologians swerving across those lines, but today it is often scientists (or science camp-followers) who are making rash assertions about what is in fact not known.  In particular, this is the case with regard to radically reductive views of human nature and the human person.

While there is no doubt that an enormous amount has been learned and remains to be learned about the nature of human beings through evolutionary biology, genetics, neuroscience, and many other branches of science, it is also true that philosophy and theology have something to say on the subject.  As Pope Pius XII emphasized, man is not simply a physical structure or biological organism, but is endowed with the spiritual capacities of reason and free will and made in the image of God. In speaking about human nature, then, theology is not trespassing into territory that belongs exclusively to natural science, but is speaking about the very heart of divine revelation.  For as Vatican II taught, Christ came not only to reveal God to man but also man to himself.  In his Angelus address on Dec 15, 1996, St. John Paul II put it this way:

“Yes, Christ is the light because, in his divine identity, he reveals the Father’s face. But he is so too because, being a man like us and in solidarity with us in everything except sin, he reveals man to himself. Unfortunately, sin has obscured our capacity to know and follow the light of truth, and indeed, as the Apostle Paul realized, it has exchanged “the truth about God for a lie” (Rom 1:25). By the Incarnation, the Word of God came to bring full light to man. In this regard the Second Vatican Council says that it is “only in the mystery of the Word made flesh that the mystery of man truly becomes clear” (Gaudium et spes, n. 22).” 17

However, in the last half century, at least, many Christian theologians and philosophers have become so intimidated that they have, as it were, pre-emptively surrendered to reductive claims about man that are, in reality, very tenuous extrapolations from what is actually known scientifically.

For example, there has been a tendency for several decades among some theologians to retreat from the traditional Christian teaching that human beings possess a “spiritual soul” distinct from — though not separate from — the body.  One can even see this in the first translations of the Mass from Latin into English in 1970, where, for example, “et cum spiritu tuo” was translated not as “and with your spirit” but simply as “and also with you”, and “sanabitur anima mea” was translated not as “my soul will be healed” but as “I will be healed.” Partly, this retreat has been motivated by the idea that the body-soul distinction was imported into Christian thought from Greek metaphysics and is alien to the original biblical conception of man as a unity.  And partly it has been motivated by the belief that modern science is moving inevitably toward an ultimate explanation of everything in terms of matter, which would leave no room for an immaterial soul.

I would argue that this is a profound misreading of twentieth century science.  But that it is also a profound misreading of Christian revelation was emphasized by Pope St. John Paul II in a number of his writings and addresses. In a general audience on April 16, 1986, he said the following:

“Man created in the image of God is a being at the same time corporeal and spiritual, that is, a being that from one point of view is linked to the material world and from another transcends it. As a spirit, as well as a body, he is a person. This truth about man is the object of our faith, as is the biblical truth about the constitution in the “image and likeness” of God; and it is a truth that has been constantly presented throughout the centuries by the Magisterium of the Church. …

It is often said that the biblical tradition emphasizes above all the personal unity of man, using the term “body” to designate the whole man. This observation is accurate. But this does not mean that the duality of man is not also present in the biblical tradition, sometimes very clearly. This tradition is reflected in the words of Christ: ‘Do not be afraid of those who kill the body and cannot kill the soul; rather fear him who can kill both soul and body in hell.’ …

[T]here is no doubt that the doctrine on the unity of the human person and at the same time on the body-spirit duality of man is fully rooted in Sacred Scripture and Tradition.”

I think this point is of fundamental importance to faith-science discussions.  I have discussed how the physical universe points to God; but just as important is that man himself also points to God, for man is the image of God.  It is by reflecting upon man’s spiritual nature, in particular our reason and free will, that we learn something about God, because, as Scripture says, “God is Spirit” (Jn 4:24).  The human spiritual powers of intellect and will are the only realities empirically accessible to us that transcend matter and thus point to the possibility of other realities that transcend the physical world, including God.  This is vital in counteracting the materialism that is the basis of so much atheism today.

It is also vital for another reason. As Pope St. John Paul II wrote in a 1996 address to the Pontifical Academy of Sciences,

“[Any theories that] consider the [human] spirit as emerging from the forces of living matter or as a simple epiphenomenon of this matter, are incompatible with the truth about man. They are also incapable of establishing the dignity of the person.”

Having lived under the two dehumanizing ideologies of Nazism and Communism, both based on the denial of the “truth about man” and both destructive of the “dignity of the person,” Pope St. John Paul II saw clearly how much is at stake in some of the discussions among scientists, philosophers, and theologians in modern times.


1.. This is quoted in section 292 of the Catechism of the Catholic Church.

2.. The Faith of the Early Fathers, trans. William A. Jurgens (Collegeville, MN: Liturgical Press, 1970), passage 747.

3.. For several more examples, see the article “God and Cosmic Order”, by Stephen M. Barr, on the SCS website.

4.. See the article “Christian Foundations of the Idea of Laws of Nature”, by Peter Harrison, on the SCS website.

5.. St. Augustine, Enarrationes in Psalmos, 45, 7 (PL 36, 518).

6.. St. Augustine, On the Literal Meaning of Genesis (De Genesi ad Litteram), trans. John Hammond Taylor, in Ancient Christian Writers: The Works of the Fathers in Translation, no. 41 (New York: Newman Press, 1982) 1:42-43.

7.. Quoted in Giorgio de Santillana, The Crime of Galileo (Chicago: Univ. of Chicago Press, 1955) 99-100.

8.. See the discussion of primary and secondary causality in the article “Why Evolution is Not a Problem for the Catholic Church”, by Stephen M. Barr, on the SCS website Also see paragraphs 306-8 of the Catechism of the Catholic Church.

9.. Francisco Suarez, De opere sex dierum, II, c. x, n. 13).

10.. See and

11.. Ronald L. Numbers (2003). “Science without God: Natural Laws and Christian Beliefs” in When Science and Christianity Meet, edited by David C. Lindberg and Ronald L. Numbers. Chicago: University of Chicago Press, p. 267.

12..  See the biographies of “Important Catholic Scientists of the Past” on the SCS website. As the great mathematician Augustin-Louis Cauchy (1789-1857) declared “I am a Christian, that is to say, I believe in the divinity of Jesus Christ as did Tycho Brahe, Copernicus, Descartes, Newton, Fermat, Leibniz, Pascal, Grimaldi, Euler, Guldin, Boscovich, Gerdil; as did all the great astronomers, physicists, and geometricians of past ages: nay more I am like the greater part of these a Catholic.”

13.. Encyclical Letter Providentissimus deus of Pope Leo XIII (Nov 18, 1893), par. 18.

14.. Pope Pius XII, “The Proofs for the Existence of God in the Light of Modern Natural Science,” Address to the Pontifical Academy of Sciences, Nov. 22, 1951.

15.. Short accounts of Georges Lemaître’s contributions can be read here and here

16..  Gaudium et spes, paragraph 36.

17.. Pope St. John Paul II, Angelus Address, Dec. 15, 1996.






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