Pope Benedict XVI’s homily at Regensburg

On 12 September 2006, on the occasion of a Eucharistic Celebration in Regensburg (Germany), Pope Benedict XVI gave a beautiful and thought-provoking homily that we would like to comment on, as a simple homage, focusing on the question that the Pope posed and to which he gave an answer: is it reasonable to believe in God?

These were his words in relation to this important issue:

We believe in God. This is a fundamental decision on our part. But again the question has to be asked: is this still possible today? Is it reasonable? From the Enlightenment on, science, at least in part, has applied itself to seeking an explanation of the world in which God would be unnecessary. And if this were so, he would also become unnecessary in our lives. But whenever the attempt seemed to be nearing success – inevitably it would become clear: something is missing from the equation! When God is subtracted, something doesn’t add up for man, the world, the whole universe. So we end up with two alternatives: What came first? Creative Reason, the Creator Spirit who makes all things and gives them growth, or Unreason, which, lacking any meaning, yet somehow brings forth a mathematically ordered cosmos, as well as man and his reason. The latter, however, would then be nothing more than a chance result of evolution and thus, in the end, equally meaningless[1].

What changed in the Enlightenment?

Since the times of Kant and Laplace, when the known universe was confined to our solar system, there has been a major shift towards materialism on the part of the scientific community.

At that time, the universe was considered static and to exist eternally. Laplace was convinced that all, absolutely all phenomena of nature, including human behavior, obeyed Newton’s laws and could be explained and predicted from them. Meanwhile, Kant argued that the universe could not be considered an ordinary object, so it would not be possible to ask about its cause, because the category of causality cannot be applied to something that is not the object of our experience. A static, eternal universe without cause fed materialist thought.

Is it possible today to think of a universe without God?

Evidently, the ideas of the cosmos held in the Enlightenment have been overcome: the Big Bang theory of an expanding universe beginning 13.8 billion years ago invalidates the foundations of thought at that time.

Nevertheless, many people maintain, time and time again, the ideas that stem from matter as the sole cause of our reality, and we must therefore consider, in the light of what science tells us, the alternatives that are presented to us.

As a premise, it can be said that science alone cannot prove the existence or non-existence of a Creator, since it is restricted to the study of the properties of our universe, but it can provide the foundation for philosophical reasoning.

Accordingly, we must review what we know scientifically about the universe and verify in light of this whether or not the idea of God is reasonable.

The universe according to the theistic understanding or the materialist understanding[2]

As a starting point, theistic thought contends that intelligence is not only a particular attribute of man, but that this attribute is the reflection of a founding mind of nature; in contrast, materialist thought holds that inert matter constitutes the fundamental reality, of which intelligence is only a derivative.

Consequently, we can deduce three conflicting traits that characterize the universe. According to theistic thought, the first would be that the cosmos can be conceived as an object (that is, as a caused entity); the second, that the cosmos is rational, as a consequence of being the product of divine reason; and the third trait, that in the universe there is purpose and one of the ends is the generation of intelligent beings, capable of knowing God and relating, in a certain way, to Him. In contrast, from the materialist idea are derived the opposite traits: the cosmos cannot be conceived as an object; the rationality of the cosmos is apparent, or must be considered a brute fact; and the cosmos pursues no end.

What we know about the universe

The way we understand the universe rests on our understanding of its physical laws, and in particular, of our understanding of the two great theories forged in the last hundred years: the theory of relativity, which describes the behavior of gravity on a cosmic scale and defines the spacetime structure of the universe; and the standard model of particle physics, which reflects all the knowledge we have about how matter acts at its most elementary levels.

The history of the universe can be said to be a thermal history: it was born as a great concentration of energy at an incredibly high temperature that expands and cools, giving rise to different changes of energy to matter. From this whole process that began 13.8 billion years ago, we can highlight several characteristics:

  • All the processes of transformation of energy and matter that occur are described by the equations that science has been developing since the beginning of the twentieth century.
  • Three minutes after the Big Bang, all the matter in the universe was already generated, albeit only in the form of hydrogen ions and some helium.
  • After 300,000 years, the hydrogen and helium atoms are formed and photons are released.
  • The stars are born, have a certain lifespan and die when they consume the fuel for nuclear fusion reactions.
  • These nuclear reactions are producing the different elements of the periodic table that we know. The larger stars die causing a large explosion that hurls all their matter into space.
  • The matter that exists in space, permanently subjected to the action of gravity, is concentrated again, thus giving rise to new generations of stars and galaxies.
  • After 9.2 billion years, after several generations of stars have formed and disappeared, the remnants of supernova explosions formed our Sun and soon after, the Earth and the other planets.
  • Thus, 4.6 billion years ago the Earth was formed; 3.8 billion years ago the first cell originated; 700 million years the first multicellular organism emerged; and only 100,000 years ago, homo sapiens

Are the traits defined by theistic thinking satisfied?

We see that the universe is an evolutionary system, which responds to laws that we know, broadly speaking. We also know that the intelligent being is the product of an evolution that begins at the moment of the Big Bang. In order to achieve humans, all phases of the evolution of the universe have had to occur: the creation of matter, hydrogen atoms, stars, all the elements of the periodic table, the solar system, the Earth, life in its single-celled form and then all the evolution of life on Earth until it achieved us. Every carbon atom inside our body has been in a star before.

Aristotelian philosophy concludes that an object must have three characteristics: be determined, constitute a unit and be independent. The universe satisfies these three traits, so it should be considered an object of our knowledge. It is determined, since it represents a whole endowed with an essential structure, a specific movement, and essential traits defined by equations and cosmological parameters. It constitutes a unit, since all the components of the universe are endowed with a common motion. And it is independent, as it is a completely closed system with no environment that can influence it.

In addition, the description of the universe reveals a great rationality. In fact, science is based on the assumption that the universe is totally rational and logical at all levels.

Therefore, current scientific knowledge of the universe allows us to characterize it as an object, which requires asking about its cause, and discovers in it a great rationality, approaching the first two traits that define the theistic cosmos, according to the framework outlined above.

 “[…] science, at least in part, has applied itself to seeking an explanation of the world in which God would be unnecessary” (Benedict XVI)

Faced with the weakening of traditional materialist arguments, some scientists have sought new arguments, trying to prove the absence of a Creator. The initial period of the Big Bang that has singular importance in cosmology is known as the Planck time. This surprisingly small time interval is 10-43 seconds. After this time, general relativity can be used to describe the interaction of matter and radiation with space. In the Planck period, we do not have a theory to describe the universe. In order to analyze what happened during this interval, we need an idea that integrates the concepts of quantum physics and general relativity into a unified theory, which has so far proven elusive. So, for now, science does not tell us why there was a great explosion or what might have existed before. Nevertheless, this is no hindrance to the repeated proclamations of different ways in which the universe could have been generated from “nothing” without the assistance of a Creator. To put these statements into context, we should explain that they refer to theories that are based on the quantum vacuum, in which there are permanent fluctuations in the value of energy. On the basis of this fact, theories have been developed stating that, if one of these fluctuations is unstable, it can become very large, like a soap bubble that is inflated. Energy remains zero on average due to a balanced interaction between the positive energy of matter and the negative energy of gravity. Thus, it is claimed that the universe emerged from the quantum vacuum. As we know, however, the quantum vacuum has nothing to do with absolute nothingness, for present in it are energy, space, time and the laws of nature. What these theories involve are transformations of energy or matter, which is the only thing that physics can explain, and which, if they were true, would constitute one of the phases in the evolution of the universe.

The cosmology of the 20th century holds more surprises for us

We can express the laws of nature through a set of equations containing a certain number of constants; these equations allow us to make very precise calculations of the most elementary physical phenomena, calculations that are confirmed by experimental evidence. From the second half of the last century, science has gradually revealed a shocking lesson: we began to perceive that there is an absolutely precise “fine tuning” of many of the constants of nature and of the initial conditions of the universe with regard to the production of life.

This important discovery had its starting point in 1953, when Fred Hoyle wondered how carbon — so necessary for the existence of life — could have been produced in the universe. In the early stages following the Big Bang, only hydrogen and helium were produced, so the formation of the other elements had to take place in the stars, once these were formed. Hoyle observed that there could be one nuclear reaction in particular, the triple alpha process, which generated carbon, but with one major problem: the beryllium nucleus, which is involved in the process, decomposes in a billionth of a second into two alpha particles. Therefore, the carbon nucleus would have to have a very specific excited energy level for it to function. The large amount of carbon in the universe, which makes it possible for life forms based on this element to exist, prompted him to think that this nuclear reaction should work even though it involved an energy level in the carbon nucleus that was unknown. The existence of life led him to this prediction, met by specialists with skepticism, but which was eventually confirmed experimentally. It was shown that the existence of life in the universe is possible thanks to a precise level of energy in the carbon atom, a level such that, if one hundred thousandth of its value were deviated, the reaction would not take place. Accordingly, carbon would not be produced in the stars and the universe could not evolve creating the other elements of the periodic table. The universe would have remained an accumulation of hydrogen and helium atoms with no possibility of life.

Following this discovery, we have learned that all the constants that incorporate the complex set of physical laws that define the cosmos possess infinitesimally specific values and that, if there were the slightest deviation in any of these values, the universe as we know it could not exist, much less sustain life. In the words of Steven Weinberg: “…how surprising it is that the laws of nature and the initial conditions of the universe should allow for the existence of beings who could observe it. Life as we know it would be impossible if any one of several physical quantities had slightly different values”[3].

Once again, explanations are sought outside of the intervention of a Creator God

The probability that tuning of this nature is due to chance is beyond our understanding. From the materialist perspective, however, once again, an attempt has been made to explain this fact, and different interpretations have been proposed. The one that has the most supporters is the idea of the multiverse, according to which our universe is only one among the innumerable existing, each of which is controlled by different parameters in the laws of nature. This idea is arrived at through several different scientific models, so-called string theory or different models that use the idea of inflation. Thus it is argued that, if there are billions and billions of other universes, the fact that ours has come upon the correct combination of finely tuned laws would not be so special. Humanity could be considered a random accident.

As we can see, the materialist cosmovision defends its position at the expense of accepting a scenario of infinite unobserved, potentially unobservable entities, going beyond science to highly speculative metaphysics. Moreover, even if the multiverse models are correct, this would not eliminate fine tuning, as all of these theories require certain parameters to take particularly precise values.

Accounts about man and the universe only fit with God in mind

The evidence obtained by cosmology showing a universe with a temporal origin, great rationality, and precise tuning for life responds to the logic of a universe created by God. This is precisely what Pope Benedict conveys to us in his homily: “When God is subtracted, something doesn’t add up for man, the world, the whole universe[4]. This is what Antony Flew, the philosopher who had been a champion of atheism for fifty years, had been debating inside, just around the year 2006, and about which he had made a complete systematic, original and influential presentation. A year later he would publish his book There is a God, where he reflects on all this evidence that cosmology gives us, which led him to abandon atheism and to conclude that “my discovery of the divine has been a pilgrimage of reason”[5].

Manuel Ribes

Bioethics Observatory – Insitute of Life Sciences

Catholic University of Valencia



[1] Benedict XVI Eucharistic Celebration, Islinger Field, Regensburg, 12 September 2006

[2] Francisco José Soler Gil Mitología Materialista de la Ciencia May 2013 ISBN: 978-84-9920-187-0

[3] The BioLogos Foundation What do “fine-tuning” and the “multiverse” say about God? 04 November 2022

[4]   Benedict XVI Eucharistic Celebration, Islinger Field, Regensburg, 12 September 2006

[5] Antony Flew; Roy Abraham Varghese There is a God: How the World’s Most Notorious Atheist Changed His Mind 2007 ISBN 10: 0061335290


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