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I. The Heavens - II. A Brief History of Astronautics - III. Popes and Astronauts - IV. Space Science, Extraterrestrials and God - V. Epilogue.

Astronautics is the science of Space flight. The word was invented in 1927 by the French writer Joseph Henri Rosny, known as Rosny the Elder, and popularised by Robert Esnault Pelterie, one of the pioneers of Space exploration. Although astronautics is a matter for engineers in the same way as astronomy is a matter for scientists, it is still imbued with its own culture and traditions, human doubts and human passion. In this article we begin by reviewing the way the heavens are represented and imagined in the Bible and elsewhere; we then continue with a brief history of astronautics; before examining how different Popes have regarded Space exploration; and lastly, we consider the issue of extraterrestrial life.

I. The Heavens

Many religions preserve traces of the worship of a divine personification of the sky or a Supreme Being residing there. Indeed, religious historians have often pondered whether awe of Uranus – the Greek god of the sky – might not underlie religious sentiment. Mircea Eliade speaks of “the almost universal belief in a divine celestial Being as the creator of the Universe and guardian of Earth’s fertility (through the rains He sends down from the sky)”. In this sense, he adds, there must be a primitive religious experience that is in no way related to speculation, imagination and myth, but is immediately perceivable to the human consciousness through sacred or divine revelation. “The sky, through its mere existence, ‘symbolizes’ transcendence, strength and immutability. It exists because it is higher, infinite, immutable and powerful.” He concludes: “Consequently, everything that occurs in sidereal space and the upper regions of the atmosphere —the rhythmical revolutions of the stars, the passing of clouds, storms, lightning, meteors and rainbows— is a moment in this same hierophany” (Eliade, 1949, pp. 47-49). Perhaps Eliade errs on the side of dogmatism or is too quick to generalize. Is it not an exaggeration to interpret all contemplation of blue skies or the star-studded celestial vault as the first signs of a religious experience? When Saint-Exupéry writes in Wind, Sand and Stars: “The most marvellous thing is that, there, standing on the planet’s arched back, between this magnetic cloth and the stars, was a man’s conscience in which the falling dust could be reflected as in a mirror. […] I was but a mere mortal lost between sand and stars, aware simply of the sweet pleasure of breathing” (Saint-Exupéry, 1939, pp. 72-74), he makes no reference to religion but appears rather to be attempting to locate and name “ethereal nothings” (Shakespeare). The link between Sky and Earth is nonetheless established; both are often understood as the two halves of the primitive Egg that gave birth to our world.

Under the Egyptian tradition of Heliopolis, Nut, the sky-goddess, was the fruit of the union between Shu, the divine male principle, and Tefnut, the divine female principle, to be set as a vault over the Earth, her brother the god Geb. Mesopotamian traditions seem to respect the “divine personality” even more: the sky-god, who inhabits the heavens but is not directly identified with them, is the supreme god, the god of gods. In the Akkadian saga, the Enuma Elish (the title being the first words of the story, “When in the height...”), the god Marduk vanquishes Tiamat, the god of the primeval salt waters and uses one half of Tiamat’s body to form the heavenly vault, sets the stars in their places and entrusts the Moon to measure out the months and the Sun to manage the turning year. According to Mesopotamian cosmology, the universe is divided into a Heaven (the Above) and a Hell (the Below); with gods who reside Above, and also Below. Between them lie the Sea and the Earth, belonging to the gods but granted to Mankind to exploit their resources.

The sky sometimes designates divine power or a deity (even the Bible sometimes uses the term Heaven in place of God of Heaven), because it is the seat of deities, but it is also the dwelling place of the blessed: the heavens are ordered according to a hierarchy of successive spiritual states. For example, guardian spirits (called “little green men” in some places!) and shamans use passages near the Pole Star from one heaven or world to another. Shamans also bring back the souls of sick people and take those of the dead or sacrificed animals, and establish contact with spirits and their god through these passages.

The authors of the Bible, like their readers, lived in a similar cultural and mythological context; they were just as conscious of the charm and fascination of the heavens, particularly the oriental heavens. However, they were careful not to assimilate, or worse still to confuse, the heavenly and the divine; the best-known illustration is probably the way they relegated the Sun and Moon to being simple lights in the sky, created only on the fourth day in the first account of the creation in the book of Genesis. Does this mean that the heaven has only a secondary and purely decorative place in the Bible’s creation story? When the God of the Bible creates, unleashing His omnipotence, He brings into being outside Himself a reality that had no existence of any kind beforehand; the Christian tradition speaks of creation ex nihilo (from nothing). Many images have been used to represent and explain the act of creation; the story of the potter is no doubt one of the best-known. The Heptameron, the account given in the first chapter of the Book of Genesis of creation over seven days, uses a different image, that of separation: God creates by separating. And the heavens have a central place in this version of the creation story.

We may suppose that the expression “Heaven and Earth” is used primarily to designate the whole of the newly-created reality. But at the same time it introduces the principle of separation that dominates the theological tradition underlying the creation story: on the first day, “God divided the light from the darkness. And God called the light Day, and the darkness He called Night.” (Gn 1:4-5). Then, on the second day, God made the firmament and divided the waters which were under the firmament from the waters which were above the firmament” (Gen 1:6-7). And separation occurs again in the first book of Genesis, concerning the creation of living beings, the grass and the fruit trees, the beasts of the fields and the fowl of the air, each one created, separated and distinguished “after its own kind”.

It is important to note that God does not create by cutting Himself off from His creation, as in a process of emanation; He creates by separating what the second Verse of the first Chapter of Genesis calls “without form and void” (as the King James Version of the Bible describes it). The lesson is plain: the separation made by God creates no sanctuaries, sacred groves or corners of divinity in the midst of reality. On the contrary, as its purpose is to be functional above all, the Creator’s work withholds from His creation, and in particular from the heavens and the heavenly bodies, any pretension to divinity: they are all formed from the same primeval chaos. The heavens are in no way any more divine than the Earth, which is itself only a kind of twin of the firmament. While the heavens are placed “in the midst of the waters [to] divide the waters from the waters,” the Earth also counterbalances the mass and the power of the waters; the Earth shares with the firmament the properties of extent and solidity. This is why the Book of Job says that when God laid the foundations of the Earth “the morning stars sang together, and all the sons of God shouted for joy.” (Job 38:7). The heavens are not alone in deserving praise; the Earth also excites wonder by challenging the pride of the waters, the last vestiges of the primeval chaos.

This chaos constantly threatens to gain the upper hand, however, to overwhelm the limits that God has placed to restrain it. We learn that at the time of the Flood “all the fountains of the great deep [were] broken up, and the windows of Heaven were opened” (Gn 7:11): the waters covered the surface of the Earth, the waters from above mingled with the waters from below; the world fell back into its primeval confusion. And God had once again to act as creator, separating the Heaven from the Earth, liquid from solid, and even adding a rainbow as a guarantee that the waters of the flood would never again ravage the Earth —at least not until the time described in the Book of Revelation, when Heaven, Earth and sea will once again be mingled.

We can therefore see that the creation myths closely associate creation, separation and de-sacralization. Even so, the authors of the Bible do not completely renounce resorting to heaven to express the seat of divinity, the realm of the Creator. Alongside the rainbow, a token of the Covenant between God and His creation, the heavenly bodies are there to measure time (and particularly to calculate the Sabbath) and to praise their Creator; but they are in no way divine: they merely perform a divine function. In the same way, the creation stories have little or nothing to say about what God is, but much more about what He does. He creates, separates, names and speaks; this is even more apparent in the second account of the creation in the Book of Genesis, where God causes it to rain, plants, works clay and breathes the breath of life. There is no comparison between the calm dependability of the heavens and the almost feverish activity of the Creator! This led someone to observe that the God of the creation stories first appears as a “traveller of the clouds” constantly on the move, doing things and giving orders. His Spirit moves even on the face of the primeval waters; and when He comes down from Heaven to deliver His son from his enemies, as in Psalm 18, He rides upon a cherub and flies upon the wings of the wind.

Strange though it may seem, in these creation stories Heaven is not God’s dwelling place, the site of a throne and the place to which all terrestrial creatures aspire like a lost homeland or a promised paradise. Strictly speaking, there is no heavenly beyond. Heaven exists primarily through the missions with which it is charged (to hold back the upper waters and rain them down on the Earth as necessary to fertilise the ground, to manage the flow of time, to praise the glory and power of God); its limits are marked by the comings and goings and the other activities performed by the Creator. It is true that in other pages of the Bible, as in the Christian tradition itself, the image of Heaven is used to represent the dwelling-place of God and the Elected. But the creation stories go to great lengths to avoid it, both to protect the way God radically transcends the condition of all of his creation and, paradoxically, to leave God free to be close to the Earth and to mankind. Long before there is any question of Incarnation, the stories show God as walking in the garden of our distant forefathers, “in the cool of the day,” or closing the door of Noah’s Ark before unleashing the Flood. By withholding any sacred or divine properties from heaven, the authors of the Bible did not distance God from his creation; on the contrary they left the way open to an incredible future event: one day God would tear open the heavens to come down to Earth as his Son and reconcile all creatures, both on Earth and in Heaven.

II. A Brief History of Astronautics

When Galileo, reporting a comment made by Cardinal Baronius, wrote in 1615 to Christine de Lorraine: “the intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes”, he was not shutting the doors of heaven to scientists and engineers. Johannes Kepler clearly understood this in 1610 when he replied to Galileo’s Sidereus Nuncius (Starry Messenger), published in April of that same year. In his Conversation with a Starry Messenger he wrote: “There will certainly be no lack of human pioneers when we have mastered the art of flight. Who would have guessed that navigation across the vast ocean is less dangerous and quieter than in the narrow, threatening gulfs of the Adriatic, or the Baltic, or the British straits? Let us create vessels and sails appropriate for the heavenly ether, and there will be plenty of people unafraid of the empty wastes. In the meantime, we shall prepare, for the brave sky-travellers, maps of the celestial bodies — I shall do it for the Moon and you, Galileo, for Jupiter.” Kepler knew “what a long road it is from a theoretical concept to its practical achievement, from the simple mention of the antipodes in Ptolemy to Columbus’s discovery of the New World, and even more from the two-lensed instruments used in this country to the instrument with which you, O Galileo, penetrated the very skies” (Koestler, 1968, p. 378).

It can certainly take a long time for theory to become practice, in this instance three and a half centuries: the first vessel to enter the heavens was Sputnik (“fellow traveller”, in Russian), the Earth’s first artificial satellite, launched by the Soviets on October 4, 1957; the first living creature was the famous dog Laika, who made the same journey on November 3 of the same year. It had taken until the end of the 19th Century and the work of the visionary Russian engineer Konstantin Tsiolkovsky for the necessary technology to appear, along with the multiple inventions that had been flourishing in the human mind for centuries. He was the first to suggest that only a liquid propellant-powered rocket (hydrogen/oxygen) would be powerful enough to break free of the Earth’s gravity field and reach other planets; he also developed the fundamental “rocket equation” demonstrating the advantages of dividing a launcher into several stages. He was unquestionably one of the principal visionaries of the future science of astronautics but, as a poor teacher with no real outside support, he never had the financial resources to carry out any experiments. He wrote two works of science fiction in an attempt to spread his ideas: Dreams of the Earth and Sky (1895) and Beyond the Earth (1920). In a letter of 1911, he wrote one of his best-known thoughts: “The Earth is the cradle of Mankind, but no-one can live for ever in his cradle.” During this same period, Robert Goddard was working on aeroplanes and rockets in the United States. On November 1, 1923, he carried out the first test of a liquid-fuel combustion chamber at the Worcester experimental centre; on March 16, 1926 he launched the first liquid propellant rocket and on April 19, 1932, the first rocket with a gyroscope and fins for stability. In 1919, he was drawn into a fierce war of words with the New York Times on the subject of propulsion in a vacuum. In a symposium in France on 8 June 1927, Robert Esnault-Pelterie gave an influential talk about “Exploring the very high atmosphere with rockets and the possibility of interplanetary travel” and in 1931 he built and tested a liquid-fuel rocket. In Germany, although Hermann Oberth may be thought of as one of the fathers of astronautics (during the 1920s he presented the world’s first doctoral thesis on Space navigation, “Rockets in interplanetary Space”), Wernher von Braun is undoubtedly far better known. He was the Director of the Peenemünde test centre where the V1 and V2 rockets were developed and was “recruited” by the Americans in 1945. He built the Redstone missile for the American Army, its first guided ballistic missile. He made a considerable contribution to the launch of the first American satellite, Explorer 1, in 1958 and joined NASA, the American Space agency in 1960, where he directed the manned flight programmes: Mercury, Gemini and, finally, Apollo which sent Neil Armstrong and Buzz Aldrin to the Moon on July 20, 1969. Armstrong spoke the now-famous words: “That’s one small step for man, one giant leap for mankind”; Kepler’s dream had come to pass and the Russian insult to America was wiped away! Even so, the subsequent manned flight programmes owed a good deal to the achievements of Soviet engineers for orbiting Space stations. NASA developed the shuttle system for travelling to and from the first human ‘residences’ circling the Earth: the Soviet Mir station and later the International Space Station. The American government now plans a return to the Moon by 2020; getting a human crew to Mars will obviously take longer.

Over the same period, Space exploration has continued using unmanned probes: the first flyby of the Moon took place in January 1959, Venus in 1962, Mars in 1965. During the  1970s the Mariner and Pioneer series of probes were launched to explore the Solar System. Telescopes were sent into Space where they could better observe the Universe: Hubble in 1990, Corot in 2006 (for the purpose of discovering new extrasolar planets). After the Viking missions in 1976, NASA succeeded in landing mobile robots on Mars in 1997 and again in 2004. Astrobiology, the science of (possible) extraterrestrial life, has become a field of study in its own right.

And lastly, since 1958, thousands of satellites have been sent up to orbit the Earth, providing observation, communication and (more recently) positioning services for the military and civil society alike. Tiros 1, the first weather satellite, was launched on April 1, 1960; a few months later, America’s Corona-14 accomplished the first spy satellite mission. The American Landsat and the French Spot programmes opened the way to civilian uses of Earth observation from Space; today, the GoogleEarth website offers increasingly clear images, which raises questions about how they can be marketed and used. Even at a time when Space tourism is becoming more and more feasible, Space activities are not governed only by military or commercial considerations: under the International Charter “Space and Major Disasters”, signed at the end of 2000, several Space agencies (including Europe, France, Canada, India and China) undertake to provide countries suffering from natural or man-made disasters with Space data or resources to help populations affected and facilitate reconstruction.

Fifty years after the launch of Sputnik, astronautics has become one of the major arenas for the struggle for power, knowledge, imagination or indeed the faith that characterises the human spirit.

III. Popes and astronauts

In September 1956, Pius XII was invited to make a speech to the Seventh Congress of the International Astronautical Federation, which was being held in Rome. It was probably one of the earliest occasions when a Pope spoke officially about Space exploration, one of humanity’s major achievements of the 20th Century, but which at the time was still in its infancy. The Pope opened by expressing his “admiration for the conviction, tenacity and daring of all those who, over the last half-century, have contributed step by step to the conquest of the immensity” of Space. Half a century because it was in 1926, recalled Pius XII, that the first liquid-propellant rocket was launched in the United Sates. He had not forgotten the military role of rockets, first used during the Second World War with the V1s and V2s, but he preferred to remember the intellectual investment required and stimulated by Space activities: “Until now, Mankind had felt like a prisoner of the Earth, with only a fragmentary knowledge of the Universe gained from whatever filtered through to him from Space, but it seems that today he has the possibility of bursting through this barrier and accessing new truths and new knowledge.” This new knowledge does not concern humanity alone but also the world and God: “The whole of God’s creation is laid before mankind, that he may constantly increase his understanding of the infinite majesty of the Creator.” However, this effort on the part of humanity, requiring all the resources of modern science and technology, must always be the fruit of international collaboration, so that the benefits may accrue to humanity as a whole: this peaceful conquest of the Universe “must contribute to making men conscious of the importance of community and solidarity, so that all may feel part of God’s great family, of being the children of one Father.” In other words, “even the most daring Space exploits must be accompanied by deep moral questioning and a heightened attitude of devotion to the overall interests of Mankind if they are not to be a cause of new conflicts on Earth.”

A few years later, John XXIII expressed very similar thoughts about Space. In 1963, the American Gordon Cooper completed twenty-two orbits of the Earth in the Mercury capsule and on 16 May in that year, in a speech before the General Council of the Pontifical Missionary Societies, commenting on his Encyclical Pacem in terris, the Pope spoke of this new breakthrough in the conquest of Space: “We pray for and bless these exploits in Space that are becoming more frequent and more technically advanced. We wish them real success and that they may contribute to brotherhood and civilisation.” He concluded with the following exhortation: “We must continue to strive, whatever the altitude, whatever the speed and whatever the technological achievements, with the determination and the confidence to bring Mankind closer to God and to spread the message of the Gospel throughout every aspect of human life.”

Paul VI said much the same: while celebrating the Feast of the Pentecost in 1965, he extended the prayer to the Virgin (the Regina Cæli) with a particular mention of the American astronauts White and McDivitt, onboard Gemini IV: “May Our Blessing cover all the Earth and rise also into the heavens for those who are now exploring new ways to the stars.” On Sunday August 29 of the same year, when saying the Angelus prayer at Castel Gandolfo, he included “a special thought for the two astronauts who are just finishing their Space flight. While hoping that under the protection of God they may successfully complete their heroic and wonderful exploit, [We consider] with admiration the constant and unimaginable progress of science and technology.” In this case it was the Americans Cooper and Conrad who were setting a new Space endurance record as part of the Gemini V mission. A year later, the Pope was on the balcony of the Vatican when he asked for prayers for Stafford and Cernan, two more American astronauts, “pioneers in the conquest of heavenly Space, these most daring representatives of the power attained by science, technology and the researches of modern man.” On December 23, 1968, when addressing his Christmas Wishes to the College of Cardinals and the Roman Curia, Paul VI praised “the ingenuity, the action and the courage of the men who dedicate themselves to this kind of conquest” and expressed a wish for “a successful and fruitful outcome to their wise and daring enterprises,” while imploring God for “assistance to the astronauts, to those working with them and to Mankind observing and reflecting on their achievements”: for the first time, men were circling the Moon. During the general audience of May 21, 1969, he spoke at length about the Apollo X mission, as part of which the L.E.M. descended close to the Moon’s surface with Stafford and Cernan on board. After the success of the Apollo XI mission when first Armstrong and then Aldrin walked on the Moon on July 21, 1969, Paul VI gave a private audience to the three astronauts, on 16 October of the same year. He told them of his admiration for their courage and the spirit of peace and of service to humanity in which they had accomplished their mission; he recalled that his prayers and the prayers of the entire Church had gone with them, and with all those who had contributed to the enterprise. The dramatic flight of Apollo XIII was mentioned during the XI Study Week of the Pontifical Academy of Sciences, in a speech by the Pope on April 18, 1970. In June 1971, while Americans were driving over the surface of the Moon in an electric jeep, three Soviet cosmonauts, Dobrovolsky, Patsayev and Volkov, died in an accident as Soyuz II was re-entering the Earth’s atmosphere. On June 30, during the inauguration of the new audience hall at the Vatican, Paul VI expressed the sorrow he felt at “the tragic and unexpected end of their enterprise that had excited so much admiration and whose sad deaths made abundantly clear the risks they ran and the heroism they showed.”

Subsequently, although John Paul II was presented on November 4, 1998 with a spacesuit by six Russian cosmonauts who had come to Rome to participate in a symposium on aging, and despite NASA’s refusal in May 2001 to allow an Italian member of the crew to carry a message from the Pope on the shuttle, papal interest in Space exploration tended more towards its philosophical and ethical aspects.

During the general audience of May 21, 1968, Paul VI was already broadening his reflections beyond the mere technological exploit: “And, as though a window had opened in our daily lives, we have an opportunity to look outside, into Space, the heavens, the cosmos. And since what we see is a human drama being acted out in the sky, our earthbound thoughts are as though captured by the emptiness that opens up before us. Our first reaction is not wonder but anxiety. An immense and mysterious reality gapes before us, that we who are not astronauts thought we could ignore because it was distant, inaccessible, something we could never experience. Now we can see deep into the outer reaches of Space, extending immeasurably before us; we can no longer escape the fact —the universe is there. On certain fine summer nights, we ourselves have perhaps contemplated the innumerable stars speckling the immense heavens; we thought, or tried to think, about the mystery of the universe. Perhaps as we looked outwards at this wonderful, mysterious vision we heard in our hearts the melancholy air sung by Leopardi’s shepherd as he wandered in the night over the wastes of Asia. Perhaps this impression of infinity, transcending both time and the infinite caused us, too, to shiver before its metaphysical implications and this ocean of being in which our life is submerged; and yet this tiny spark of life is nonetheless Life, Consciousness, Spirit.” Less than twenty years beforehand, Pius XII had been excited by the results of modern astronomy, to the extent that he enthusiastically declared: God awaits us, he said, behind every door that science opens. In his speech of 1968 Paul VI did not share the same enthusiasm of his predecessor; but he did speak, nonetheless, of this “contact with a veil behind which we can detect the breath of an infinite presence”, just as, during the Angelus of Sunday 29 December 1968, on the return of Apollo VIII he spoke of “the need for an idea of God, of his existence and his knowledge [which] becomes even more powerful.” He went on: “This overturns the mean, empirical idea that we sometimes have of God; it widens our childish thoughts to infinity and forces us to repeat, with a new and more profound sense, the Lord’s Prayer: Our Father, Who art in Heaven.” A few months later, he again said: “Since the cosmos exists, since it seems to us to be on the one hand so heavy with mystery (this is what science tells us, especially mathematics and physics; the movements and the forces and laws that we find operating out there confirm it), and on the other, as we might say, so imbued with a thought that is not its own but which is infused, reflected, effective, and understandable, knowable, available for us, that can only mean that the cosmos results from some transcendent principle, from a creative thought, from a secret and superior power …, meaning that it was indeed created” (July 16, 1969). He concluded that the discovery and observation of the cosmos would be “a modest but still a fine lesson for religious instruction,” prompting us to “see God in the world and the world in God.”

“What then is Man, if he is capable of such grandiose achievements?” wondered Paul VI, on July 20, 1969. When the Popes see mankind in the light of Space exploration, it seems to produce in them the same “metaphysical shiver” as when they consider God. Alarm and admiration: it therefore comes as no surprise that Paul VI should dedicate Psalm 8 to the Apollo XI astronauts. In the technical and scientific adventure that started in 1957 and was in full swing in the 1960s, each day sheds more light on the reality of humanity’s microscopic status in the cosmos; being so small, however, does not prevent it from possessing an extraordinary capacity for intelligence and invention, adaptation and conquest.  “Man,” said Paul VI on February 7, 1971, “though a mere atom in the Universe, is there anything he cannot do? All honour to man, to human thought, science, technology, labour and daring. All honour to the way man creates a synthesis between science and its implementation, he who, unlike all the other animals, is capable of using the tools of conquest with his intelligence and his hands. All honour to man, king of the Earth, and now prince of the skies. All honour to the living creature that we are, made by God in His image and who, by attaining mastery over His creation, obeys the commands of the Bible: ‘replenish the Earth, and subdue it.’ For centuries, man has puzzled over the great enigma: ‘Know thyself.’ Today he is taking great strides on the road to self-discovery. Man catches a glimpse of his invisible mystery within himself, of his immortal spirit, and he obeys the natural destiny that drives him to progress. This is no case of vain ambition, but a response to the vocation of his being, at the same time learning to read in the cosmos the demands of a mysterious and silent creative principle, eternal and all-powerful, that thinks and acts.” As early as the end of the 19th Century, Father Ortolan wrote: “Yes! Only the progress made by astronomy could reveal to man how great and powerful he is! No other of the inventions that have sprung from his fertile genius was capable of giving him such a high idea of his soul.” (Ortolan, 1894, 10).

While remaining aware of both its limits and excesses, the Popes who have referred to Space exploration have essentially expressed admiration for man, as in Psalm 8, or again as in the commandment from the Book of Genesis: “replenish the Earth, and subdue it.” Pius XII had used the same expression: “The Lord God, who placed in men’s hearts an insatiable desire for knowledge, did not mean to impose any limit to his striving for conquest when He said “Subdue the Earth”. He entrusted the whole of His creation to man and to the human spirit, that he may explore it and so come to understand ever more profoundly the infinite glory of his Creator” (September 20, 1956). These constant references to God the Creator, on whom all creatures depend, reflect the gradual development, through all the Papal discourses of the second half of the 20th Century, of what John Paul II called a new humanism. In other words, an approach “where spiritual, moral, philosophical, aesthetic and scientific values can develop in harmony, and where liberty and the rights of man are respected totally […] for the spiritual and materiel wellbeing of all mankind” (November 7, 1986), which inevitably implies certain ethical constraints.

Speaking to the Second United Nations Conference on the Exploration and Peaceful Use of Outer Space on August 9, 1982, Monsignor Mario Peressin chose to deal with an objection often made to Space exploration: “Are we perhaps taking this too far? Might not the conquest of Space lead the most powerful nations and the scientific community to forget our basic human problems such as the poverty and hunger of hundreds of millions of human beings, the unemployment that is spreading across the industrialised world, not to mention the chronic under-employment in the poorer countries? Should we not first concentrate on solving these dramatic problems? Might the conquest of Space be a costly and futile enterprise, as well as a dangerous diversion?” Monsignor Peressin had a clear answer: “It is vital to pursue Space exploration, in the interest of Mankind.” He did not mean only a practical interest (the prelate gave several examples of the applications of Space technology, particularly in the fields of telecommunication, meteorology and remote sensing); it can also be found in the example set by Space exploration for other fields. What did he mean, exactly? As the Catholic Church sees it, and as the above-mentioned quotations amply demonstrate, contemplating and exploring the cosmos has had and continues to have a positive influence on man’s understanding of himself. Following the success of the Apollo XI mission, Paul VI pointed out that Space exploration can be an example, particularly for young people who hear all around them the siren-song of “defeatism, so fashionable today, regarding society and modern life in general. […] Life, on the contrary, is serious, as we can see from all the studies, costs, labour, planning, trials, dangers and sacrifices required for an enterprise as colossal as Space exploration. It is easy enough to criticise and contest; it is much harder to build; in the case of Space exploration, of course, but also in the many other examples offered by civilisation today. For this reason We feel that the event we are celebrating together today obliges us to reconsider and appreciate the values of modern life. We do not deny anyone’s right to criticise, nor do We reproach young people for their natural taste for freedom and novelty. But We consider that the iconoclastic and loveless decadence exhibited by professional protesters is unworthy of young people. The young need idealism and positive values, such as those behind the magnificent adventure of Space exploration.” The different Popes have constantly highlighted and encouraged the peaceful nature of Space exploration. “This common effort by all Mankind to conquer the Universe in peace,” said Pius XII as early as 1956, “must help to raise an awareness in the minds of men of the meaning of community and solidarity.” When offering his Christmas wishes in 1962, Pope John XXIII said: “May the new year that is about to start see many more of these peaceful conquests brought about by the genius of man! And may God inspire those who organise these great space enterprises to bring together brave and capable men from every nation and every race to join in their efforts and their experiments. In this way they will work profitably for brotherhood and peace, that we all pray and wish for at this holy time of Christmas.” Paul VI had something very similar to say for the first Spacewalk, performed by the Soviet cosmonaut Leonov, orbiting in Voskhod II, in March 1965: “We wish, with all Our soul, that all this progress may serve to make men better, more united and more determined to pursue the ideals of peace and the wellbeing of all.” He said much the same thing again for the launch of the American communication satellite Early Bird, on May 3, 1965: “We pray to Almighty God that these wonderful achievements may serve the cause of peace and allow men to cooperate in making this world a better and happier place, where each can develop in the image of his Creator and find the fulfilment of his desires, as far as that may be possible on Earth.” John Paul II, finally, on June 20, 1986, before a group at the Pontifical Academy of Sciences meeting to consider the impact of remote sensing by satellite on the economies of developing countries, expressed the wish that “by means of joint agreements and commitments, all governments will promote the peaceful use of Space resources, for the sake of the unification of the human family in justice and peace.” The Pope acknowledged that certain Space missions could embody peace and harmony in their own right, such as those aiming to inspect Halley’s Comet, whose principal managers he received in December of that year; but he was well aware, no doubt to a greater degree than his predecessors, to what extent the use of Space can also turn out to be quite contrary to the wishes of peace, solidarity and brotherhood.

Paul VI, of course, was also fully aware of how much competition is involved in rival Space enterprises: not long before the launch of Italy’s San Marco II satellite, in May 1965, he spoke of “the peaceful and inspiring competition for the conquest of Space.” Again, in August 1964, when the American probe Ranger VII had just landed on the Moon, he prayed “that as mankind progresses in his conquest of the world, nature and knowledge, he does not lose his way or be overcome by pride” and does not “give way to the materialistic temptation that such progress can present, but that he may find in it new ways of understanding the grace of God Who raised us to the order of spiritual beings.” Both John XXIII and Paul VI were aware of the potential for peace of the Space ideal, and of its fragility; but they remained heavily influenced by the admiration aroused by the accomplishments of astronautics and the progress they represented. John Paul II, while not denying the usefulness of Space activities, preferred to underline the questions, indeed the rigorous ethical approach that these activities require; they are indispensable. “Modern Space technology,” warned John Paul II before the Pontifical Academy of Sciences on October 2, 1984, “must not be used by any form of cultural imperialism, to the detriment of the authentic cultures of human beings in the legitimate differences that have developed in the history of the individual peoples.” Certain themes in particular catch His attention: militarization and national sovereignty, natural resources and ecology, and intercultural exchanges.

The use of Space for military purposes is totally contrary to the provisions of the “Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies” (1967). This treaty goes so far as to say, in its Article IV, that “States Parties to the Treaty undertake not to place in orbit around the Earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner.” With prohibitions of this sort, as Monsignor Peressin remarked in his speech of August 9, 1982, international law takes on a planetary dimension, becoming in other words a law for mankind as a whole. Such a dimension finds an echo in the constitution of Vatican Council II Gaudium et spes: “God intended the Earth with everything contained in it for the use of all human beings and peoples. Thus, under the leadership of justice and in the company of charity, created goods should be in abundance for all in like manner.” (no. 69). And indeed, as John Paul II stressed in the same 1984 address to the Pontifical Academy of Sciences, now that Mankind is blessed “with your knowledge and practice of modern space technology”, thanks to which “it would be possible to work out adequate programmes for helping the world to overcome the imbalance of agricultural practices, the advance of deserts, ecological disasters caused by human rapacity against the earth, in the waters and in the atmosphere, with the ever more alarming destruction of animal and plant life, and with grave and mortal affecting human life itself.”

Sharing resources, cooperation, brotherhood: these expressions are often used in the world of Space and by those whose speeches draw inspiration from its achievements, Popes included. But everyone knows what really happens: once the research phase is over, when testing and final adjustments have been completed, when the programmes go into their operational phase, the noble intentions often tend to fade while fears and personal interest come to the fore. Threats to national sovereignty from Space applications include such controversial issues as remote sensing (the possibility of flying over and observing any part of the globe) and telecommunication (the possibility of infiltrating a country’s cultural network with impunity). Monsignor Peressin mentioned this danger: “We should constantly bear in mind two important principles: that each State has a legitimate right to independence and freedom of action, though with full respect for the rights of others based on universal inter-human solidarity; and that sovereignty is not an absolute right, giving the power to prohibit free cultural exchanges, as it should be based on the same universal inter-human solidarity.” This is one way of reminding us that technical and scientific progress not only needs to be held in check by ethical considerations but also requires changes in our minds and cultures.

IV. Space Science, Extraterrestrials and God

The question of extraterrestrial life has always caused considerable hesitancy in the scientific community. For some, the three ingredients necessary for life to appear —water, energy and organic molecules— exist in large quantities throughout the Universe. And, as the English astronomer Harold Spencer Jones wrote in 1940: “It seems reasonable to suppose that, as long as suitable conditions come together in the Universe, life will inevitably appear” (Dick 1998, p. 187). Indeed, many exobiologists and astronomers follow Sir Harold in basing their approach on the necessary, almost predestined, appearance of life or, at least, of prebiotic syntheses. After all, the Universe suffers from no shortage of either space or time. Other scientists, however, consider the chances of life appearing as low or very low. At about the same time as Sir Harold, the Frenchman Pierre Lecomte du Noüy was applying probability theory to calculate the time necessary for the formation “of a single molecule with a high degree of dissymmetry […] by random chance and thermal activity.” He concluded that “the mean time necessary to form such a molecule (with a degree of dissymmetry of 0.9) in a volume equivalent to that of the planet Earth is of the order of 10243 billion years (1 followed by 243 zeros)” (Lecomte du Noüy, 1947). And the formation of such a molecule would be only the very first stage of a process which might lead to the development of the human species, via all the random circumstances of evolution! When such levels of probability are considered, the appearance of life on Earth seems such an unlikely occurrence that it could only be unique. The French biologist Jacques Monod came to the same conclusion and based a philosophical lesson on it in his book Chance and Necessity: “The old alliance has been broken; Man at last knows that he is alone in the unfeeling immensity of the universe, out of which he emerged only by chance. Neither his destiny nor his duty have been written down. The kingdom above or the darkness below: it is for him to choose.” (Monod, 1972, p. 167).

Francis Drake and Enrico Fermi have each summarised these alternatives in their own way. Drake suggests a formula for calculating the number of civilisations that could exist in our galaxy (the Milky Way) and with which we might hope to communicate. His formula is set out as follows:

N= R x fp x ne x fl x fi x fc x L

where N is the number of civilisations; R is the rate of annual star formations in the Milky Way; fp is the fraction of these stars that have planets; ne is the average number of planets similar to our Earth (potentially able to support life); fl is the fraction of such habitable planets on which life might develop at some point; fi is the fraction of planets bearing life forms that evolve into intelligent creatures; fc is the fraction of these intelligent life forms capable of communicating with the Universe; L is the average lifetime of a civilisation capable of communicating with the Universe.

When Drake postulated this formula at the Green Bank conference in 1963, it rapidly became a benchmark, particularly for those in favour of a research programme to detect the existence of extraterrestrial intelligence, the SETI programme (Search for Extra Terrestrial Intelligence). Several authors calculated their own values for N. In 1963, Carl Sagan, for example, suggested 106; in 1981, other scientists reduced this to 0.003.

A decade earlier, during a lunch with colleagues at Los Alamos, the Italian physicist Enrico Fermi, who had received the Nobel Prize in 1938, asked a question that became known as the Fermi Paradox: “If extraterrestrials exist, where are they? [...] There are 200 billion stars in our Galaxy, most of them Type I, meaning that they were formed at the same time as the Galaxy 10 billion years ago. Our Sun and its retinue of planets were formed in turn less than 5 billion years ago. Life appeared after barely one billion years and our technological civilisation 4 billion years later. It is therefore possible for an intelligent and technologically-advanced civilisation to develop on a planet in no more than 5 billion years. Since the Galaxy is 10 billion years old, technological civilisations may well have appeared 5 billion years ago. Since it need only take a few hundred million years to develop the technologies necessary for visiting or colonising the entire Galaxy, they could have been around for billions of years already. But they’re just not there.” (quoted in Arnould, 2004, p. 137).

Apart from scientists, many other thinkers have made connections between belief systems or creeds and statements about extraterrestrials, inhabited worlds, UFOs and Unidentified Aerial Phenomena or UAPs (Renard 1988; Jung 1961; Stoczkowski 1999). In his book UFOs: God’s Chariots?, Ted Peters studies beliefs about UFOs and their links with politics, science and religion (Peters, 1977). He notes the characteristics of extraterrestrials usually associated with heavenly divinities: transcendence, omniscience, perfection, the power of redemption. Don’t they come from Heaven? Don’t they claim to have created us? Aren’t they constantly watching us, our actions, our thoughts, with what the Ancients called “the all-seeing eyes of the gods”? Do they not possess perfect knowledge, together with physical beauty (some of them, at least) and wisdom? Have they not discovered the secret of immortality that they might be persuaded to share with Mankind if we could only renounce evil and the will to destroy? Like gods, in fact, do they not appear only to a privileged elect few, preferring to remain hidden from ordinary mortals? The French sociologist Jean-Bruno Renard has noted that some go so far as to attribute a Messianic role to extraterrestrials or expect that they will usher in a millenarist New Age. “Belief in the imminent arrival of extraterrestrials on our planet is a fundamental characteristic of flying-saucer enthusiasts. […] Extraterrestrials landing here would not have as their sole mission the salvation of an elect few. They would also be here to set up a new era of peace and happiness on Earth, after a period of trial.” (Renard, 1988). Defenders (or worshippers?) of extraterrestrials and UFOs, just as extremist in my opinion, don’t hesitate to seek (and find) arguments in favour of the existence of extraterrestrial vessels, beings and civilisations in sacred or hagiographic writings. Erich von Däniken, author of the best-selling Erinnerung an die Zukunft (1968) developed a theory explaining that God and his angels were beings from other planets and that their miracles were accomplished with the help of advanced technologies. When the Book of Genesis tells of the union between the daughters of men and the “sons of God”, von Däniken suggests that the latter were extraterrestrials. Noah’s Ark, the vision of Ezekiel or Elijah’s fiery chariot, familiar to readers of the Bible, are all interplanetary spacecraft. The destruction of Sodom and Gomorrah is the result of an atomic bomb; the Walls of Jericho are brought down by a “high-powered generator of infrasound”. And so on … Von Däniken and his supporters, the “Dänikenians,” with their excessively literal reading of sacred texts and religious myths, ignore or reject the analytical approach that in some cases has been carried out for centuries. This is a very revealing failure on their part, because documentary criticism is itself a scientific process; it also stops short of claiming to develop a definitive interpretation of scriptural or religious “reality” which always remains partly shrouded in mystery; it merely tries to provide a more informed basis for belief and faith, not proof in any form.

Far from the somewhat outlandish views recalled above, historians, theologians and philosophers have long pondered over the question of extraterrestrial life (extended reviews in Crowe, 1999; Dick, 1982; Dick, 1998).

One of the most famous traces of such an interest can be found in the syllabus published by the Bishop of Paris, Etienne Tempier, on March 7, 1277. The ecclesiastical authorities of Paris condemned 219 propositions, one of which was expressed as follows: “That the First Cause could not create several worlds.” By rejecting the idea that our world was necessarily unique, one might say that the Church signed the birth certificate of extraterrestrials —at a time when the inhabitants of the Americas had not yet been “discovered”! A few years earlier, in 1270, Tempier had already criticized the fashion for rationalism that had swept over the University of Paris, in the form of radical Aristotelianism; at that time, the bishop condemned several propositions: the idea that the world is eternal, universal determinism and above all that revelation could be contradicted by reason. However, it must be said that Bishop Tempier’s warning was aimed at defending, and on a theoretical basis, the universal power of God, so that it has no direct relationship with ET, at least as we face the issue today.

As Albertus Magnus saw it, the question of the plurality of worlds was one of the noblest questions Mankind had to address; a question, as he insisted, for which Mankind needed to find an answer absolutely, which is what his most famous pupil, Thomas Aquinas, tried to do. Aristotle’s views on heaven were both stimulating and problematical to Christian theologians. Aristotelian geocentrism, especially if extrapolated to anthropocentrism, was attractive to the Christian tradition, especially with its above/below — perfect/imperfect typology that matched the Christian view of Creation. More troublesome, however, was Aristotle’s affirmation about the uniqueness of our world. If we accept that God is the creator, how can we reconcile the idea of one unique world with the very real diversity of the creatures created and His reputed omnipotence? How could God be restricted in his generous and prodigious work of creation? And by whom? In his Summa Theologica (cf. I pars, qq. 44-48) Thomas Aquinas answers as follows: 1. God has produced multiple and various creatures “so that any attributes lacking in one to represent divine goodness may be supplied by another”; diversity is therefore the work of God alone and not “from the chance coming-together of a plurality of causes”; 2. The wisdom of God, which has caused beings to be different from one another, has also caused them to be unequal. This is not the result of some kind of conflict between the forces of good and evil, a “Fall” or original sin; again, its essential cause can be found in God. If there really is a hierarchy amongst His creatures, it is not for the benefit of a privileged few or of despots, but is there for the sake of the harmony of the whole; 3. All creatures necessarily belong to a single world. If we admit a plurality of worlds, we must also admit the existence not of a controlling wisdom but of chance: we must therefore affirm that the world is unique.

Distinction (and multitude), inequality, unity: the three principles posited by Thomas Aquinas rest on the premise that God alone is at the origin of all things. The Dominican noted that some writers support the idea that the perfection of the Universe (which depends in particular on the diversity of the creatures in it) could be the result of pure chance, especially as God, as oneness personified, could not create multiplicity. On the contrary, counters Brother Thomas, nothing short of such variety could possibly confer on the whole of divine creation even a partial reflection of divine goodness, in its simplicity and uniformity. In other words, recognising a unique God by no means prevents but rather invites or obliges us to accept and contemplate the diversity, the richness and the multitude of the forms taken by living things.

In the 15th Century, Cardinal Nicholas of Cusa again raised the question of the existence of inhabitants on other planets and the hierarchical system they must be a part of, which he attributed to the “physical” nature of whichever celestial body they lived on. In his Docta Ignorantia (1439), he wrote: “It may be conjectured that in the area of the Sun there exist solar beings, bright, enlightened, intellectual and by nature more spiritual than such as may inhabit the moon — who are possibly lunatics — while those on Earth are more coarse and material; so that the more intellectual creatures that inhabit the Sun are more given to action than to power, whereas the inhabitants of the Earth are more given to power than to action; as for those who live on the Moon, they are somewhere between these two extremes. These opinions are suggested to us by the influence of the Sun, which is by nature fiery, by that of the Moon, which is made of air and water, and by the heaviness of the Earth. The same is no doubt true of the other stars, for we see no reason to suppose that they are uninhabited.” (Book II, ch. XII). Certainly, the Cardinal (who attended the Councils of Bâle and of Florence) was reflecting the cosmology of his time; but he has no hesitation about wondering whether the trajectory of the planets is really circular, nor of applying to the cosmos the expression used by the Stoics to define divinity: “A circle whose centre is everywhere and whose circumference is nowhere.”

During the same period, William Vorilong, who also had no difficulty with the idea that God could create an infinity of worlds, including worlds superior to our own, questioned what a plurality of worlds meant for Christology. As to the question of whether Christ by dying on this Earth could redeem the inhabitants of another world, William Vorilong answered that “He is able to do this even if the worlds are infinite, but it would not be fitting for Him to go into another world that He must die again” (quoted in Dick, 1982, 43).

By defending the hypothesis of a plurality of worlds, the condemnation of 1277 left the idea of humanity’s supremacy in the Universe, of cosmic anthropocentrism, intellectually bankrupt. The Copernican Revolution, the passage of Western thought from a closed world to an infinite universe, provided a scientific basis for the position held by Etienne Tempier’s syllabus. Standing at the threshold of the modern era, the Revolution affected not only astronomy but spilt over into theology as well. Whereas with Thomas Aquinas, the debate concerned primarily the theology of creation (in other words the manner in which the faithful understand the world and God’s behaviour towards it), the modern era, particularly under the influence of Protestant ideas, concentrates more on the individual, his salvation, and as a consequence, on Christological issues. Would God need to redeem any life forms that might exist on other planets? These changes are clearly shown in the thoughts of the theologians when they ask such questions as: Why should faith or theology be troubled by the possible existence of extraterrestrial lifeforms? Does the Earth necessarily have a monopoly on intelligent life? Are extraterrestrials subject to Original Sin or do they live in a state of grace, with no need of Christ’s Redemption?

Teilhard de Chardin, the Jesuit who died in 1955, too early to see the first interplanetary Space missions, wrote: “the idea that only one planet might be populated in the entire Universe has become just as unthinkable for us (insofar as we think about it at all) as the idea of Mankind appearing on Earth with no genetic connection to the other creatures of the Earth. [...] With such a prodigious plurality of celestial sites of ‘immortal life’, how will Theology respond to the expectations and hopes of all those who wish to continue worshipping God in spirit and truth?” (Teilhard de Chardin 1969, pp. 277-278). He warns against three facile solutions: deciding that, of all the inhabited planets, Earth alone knew Original Sin and needed to be redeemed; imagining that Christ’s redemption of man, accomplished by his Incarnation on our planet, is somehow known to all other ‘Humanities’; and lastly, affirming that the Earth is the only inhabited place in the Universe. You don’t need a doctorate in theology, Teilhard de Chardin concludes, to see that these solutions are hardly convincing. So what can be done? We should open up theology to the possibility of extraterrestrial beings, without necessarily seeking to develop a theology adapted for use on these new worlds. And, as our Jesuit palaeontologist saw it, this means taking very seriously the convergence between the Universe and Christ’s universality, even if to do this we must be prepared to revise our theological representation of “Creation”.

Sister Ilia Delio, a Franciscan theologian, offers an example of such a revision in her suggestion for “exoChristology” (Delio, 2007). She responds to the concerns of theologians and believers, worried by the question of the salvation of extraterrestrials, by going back to the theology of Bonaventure and Duns Scotus who stressed the presence of Christ in the heart of every creature, rather than the necessity of the Incarnation for the redemption of sinners. Why should we strive to imagine alien Christs, when our only way of envisaging God is based on Man? The Incarnation, suggests Ilia Delio, should be considered above all as a theological event and not an anthropological one. The Word of God, she says, is personified in the different orders of intelligent creatures, while remaining unique. Such a theological perspective is a fruitful subject for many lines of debate and highlights the value of pursuing the old reflection of a theme rediscovered in the 20th Century, that of the Cosmic dimension of Christ.

V. Epilogue

An experience of emptiness on the one hand, an experience of God on the other: whether in Space, or confronted by Space, the believer cannot avoid facing up to reality. The mystery of God the Creator and the Saviour; the mystery of one’s own nature, partly divine yet at the same time profoundly rooted in the very physical soil of this Earth. The relationship between humans and the Earth seems very strong, and even if the ashes of a famous astronomer now lie on the surface of the Moon, many Earth-dwellers are probably a long way from imagining that they could one day leave their planet for ever, including after death: at the height of the Apollo XIII drama, the three astronauts had requested that every effort be made to bring their bodies back to Earth. Until we have those future colonies on the Moon or even Mars, the only way for humans to experience Space will necessarily include a return to Earth. This is not the least of the lessons that Space holds out for humans.


J. ARNOULD, La lune dans le bénitier. Conquête spatiale et théologie (Paris: Cerf, 2004); M.J. CROWE, The Extraterrestrial Life Debate, 1750-1900 (Mineola, NY: Dover Publications, 1999); I. DELIO, “Christ and Extraterrestrial Life”, Theology and Science, 5 (November 2007), pp. 249-265; S.J. DICK, Plurality of Worlds. The Origin of the Extraterrestrial Life Debate from Democritus to Kant (Cambridge: Cambridge University Press, 1982); S.J. DICK, Life on Other Worlds. The 20th-century Extraterrestrial Life Debate (Cambridge: Cambridge University Press, 1998); P. DUHEM, Le Système du monde. Histoire des doctrines cosmologiques de Platon à Copernic, tome X (Paris: Hermann, 1965); M. ELIADE, Traité d’histoire des religions (Paris: Payot, 1949); C. FLAMMARION, La Pluralité des Mondes habités (Paris: Editions Didier, 1864); C G. JUNG, Ein moderner Mythus (Zürich: Rasher Verlag, 1961); A. KOESTLER, The Sleepwalkers: A History of Man's Changing Vision of the Universe (London: Pelican, 1968); A. KOYRÉ, La Révolution copernicienne (Paris: Hermann, 1974); P. LECOMTE du Noüy, Human Destiny (New York; Longmans, Green and Co., 1947); J. MONOD, Chance and Necessity: An Essay on the Natural Philosophy of Modern Biology (London: Fontana, 1972); Th. ORTOLAN, Astronomie & Théologie ou l’erreur géocentrique, la pluralité des mondes habités et le dogme de l’Incarnation (Paris-Lyon: Delhomme et Briguet, 1894); J.-B. RENARD, Les extraterrestres. Une nouvelle croyance religieuse? (Paris: Cerf, 1988); T. PETERS, UFOs: God’s Chariots?: Flying Saucers in Politics, Science, and Religion (Atlanta: John Knox Press, 1977); J.-B. RENARD, Les extraterrestres. Une nouvelle croyance religieuse? (Paris: Cerf, 1988); A. DE SAINT-EXUPÉRY, Terre des hommes (Paris: Gallimard, 1939); W. STOCZKOWSKI, Des hommes, des dieux et des extraterrestres. Ethnologie d’une croyance moderne (Paris: Flammarion, 1999); P. TEILHARD DE CHARDIN, La multiplicité des mondes habités (5 juin 1953), in, “Œuvres”, v. 10 (Paris: Seuil, 1969).

Sources for the Papal Addresses: Collection of Teachings of Pius XII, Discorsi e Radiomessaggi di Sua Santità Pio XII, 20 vols. (Vatican City - Milan : LEV and Vita e Pensiero, 1941-1959); Collection of Teachings of the Popes, Paul VI (1963-1978) and John Paul II (1978-2005), Insegnamenti (Vatican City : LEV, 1963-2005); Benedict XV - John Paul II, Papal Addresses to the Pontifical Academy of Sciences (1917-2002) and to the Pontifical Academy of Social Sciences (1994-2002), “Pontificiae Academiae Scientiarum Scripta Varia”, n. 100 (Vatican City: LEV, 2003).