Extraterrestrial Intelligence and the Catholic Faith: Are We Alone in the Universe with God and the Angels?

By Paul Thigpen

For more than half a century, the question of extraterrestrial intelligence (ETI) has been widely dismissed in our culture. That wasn't always the case. Some of the best minds of the last twenty-five centuries in Western civilization have grappled with this mystery.

In Extraterrestrial Intelligence and the Catholic Faith, best-selling author Paul Thigpen begins with a fascinating historical survey of the public conversation about ETI, tracing the thought of prominent Catholics and others. Well-known figures such as Plato, Saint John Chrysostom, René Descartes, Isaac Newton, Benjamin Franklin, Réginald Garrigou-Lagrange, and C. S. Lewis all speculated about the possibilities of life beyond our planet. Even Catholic saints and blesseds spoke of ETI, such as Pope Saint. John Paul II, Saint (Padre) Pio of Pietrelcina, and Blessed Anne Catherine Emmerich.

In light of this history, readers will discover answers to these questions:

How do Scripture and Catholic teaching shed light on this topic?

Are alleged encounters with ETI simply a form of demonic deception?

Is belief in ETI compatible with the Catholic Church's teaching?

What might be the spiritual and moral status of ETI, and what relationship might they have to Jesus Christ?

Would the confirmed existence of ETI undermine the Christian faith, as some have claimed?

How can thinking about ETI deepen our faith and enhance our understanding of the Church's teaching about God and His creation, Jesus Christ and salvation, and God's ultimate intention for His creatures?

Still more, a concluding appendix addresses the related issue of unidentified flying objects (UFOs) and the speculation surrounding them. Recent developments in astrophysics, technology, and UFO-related disclosures by the Pentagon have reawakened the public discussion about ETI. Extraterrestrial Intelligence and the Catholic Faith is a thorough guide to navigating the conversation from a faithful Catholic perspective.

• Language: English
• Publisher: TAN Books
• Release date: Jun 28, 2022
• ISBN: 9781505120158

Book preview

coverimage

EXTRATERRESTRIAL

INTELLIGENCE

and the

CATHOLIC FAITH

EXTRATERRESTRIAL

INTELLIGENCE

and the

CATHOLIC FAITH

Are We Alone in the Universe

with God and the Angels?

PAUL THIGPEN

TAN Books

Gastonia, North Carolina

Extraterrestrial Intelligence and the Catholic Faith: Are We Alone in the Universe with God and the Angels? © 2022 Paul Thigpen

All rights reserved. With the exception of short excerpts used in critical review, no part of this work may be reproduced, transmitted, or stored in any form whatsoever, without the prior written permission of the publisher. Creation, exploitation, and distribution of any unauthorized editions of this work, in any format in existence now or in the future—including but not limited to text, audio, and video—is prohibited without the prior written permission of the publisher.

Unless otherwise noted, Scripture quotations are from the Revised Standard Version of the Bible—Second Catholic Edition (Ignatius Edition), copyright © 2006 National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved.

Cover design by David Ferris—www.davidferrisdesign.com.

Cover image: Old church in Sarja (Belarus) under the starry sky, © Viktar Malyshchyts, Shutterstock.com

Library of Congress Control Number: 2022934854

ISBN: 978-1-5051-2013-4

Kindle ISBN: 978-1-5051-2014-1

ePUB ISBN: 978-1-5051-2015-8

Published in the United States by

TAN Books

PO Box 269

Gastonia, NC 28053

www.TANBooks.com

For my dear friend and esteemed colleague

Conor Gallagher,

who in so many ways

has made this book possible,

and in memory of

John Moorehouse,

beloved editor and friend.

He, who thro’ vast immensity can pierce,

See worlds on worlds compose one universe,

Observe how system into system runs,

What other planets circle other suns,

What vary’d Being peoples ev’ry star,

May tell why Heaven has made us as we are.

ALEXANDER POPE, An Essay on Man

Contents

Acknowledgments

Do You Know the Ordinances of the Heavens?

An Introduction to the Conversation

I. A History of the ETI Conversation

1. Worlds without Number

A Lively Debate since Ancient Times

2. One of the Most Wondrous and Noble Questions

The Medieval and Early Renaissance Debates

3. A Thousand Labyrinthes

The Later Renaissance Debates

4. Awake Up the Eyes of Your Understanding

Enlightenment Thinkers Take up the Conversation

5. Against the World-Mongers

ETI Skeptics Strike Back

6. A Blasphemy to Doubt It

ETI Debates of the Nineteenth Century

7. Globes of Gold or Diamond

Voices of Catholic Poets and Priests

8. They Are Children of God as We Are

Voices of the Twentieth Century

9. Intelligent Creatures in a Billion Galaxies

A Twenty-First-Century Renewal of the ETI Conversation

II. A Contribution to the ETI Conversation

10. Nothing Is Impossible with God

Is ETI Compatible with Catholic faith?

11. God Shield Them from Us!

Possibilities for the Spiritual and Moral Status of ETI

12. The Great Physician May Have Applied Different Remedies

Paths to Redemption for ETI?

13. A Million Alien Gospels

Multiple Incarnations for ETI?

14. A New Heaven and a New Earth

Paths to a Final Destiny for ETI?

The Outskirts of His Ways

An Epilogue to the Conversation

What about UFOS?

Thoughts about Unidentified Flying Objects

Bibliography

Index of Scriptural References

Index

Acknowledgments

I wish to thank …

•Conor Gallagher, my dear friend and publisher at TAN Books, who invited me years ago to write this book, and who had the courage and foresight to publish it.

•My dear friends Brian Kennelly, Mara Persic, Caroline Green, Nick Vari, and all the wonderful folks at TAN who have been so patient with me and worked hard to see this book become a reality.

•Taynia-Renee Franche d. Laframboise, a faithful Catholic scholar with interests similar to mine who has encouraged me in this study and who has important things to say about this subject.

•Marie I. George, PhD, another faithful Catholic scholar who kindly sent me a copy of her book Christianity and Extraterrestrials some years ago when I expressed interest in it; her work has made an enormous contribution to my study.

•Daniel Hynes and Stephen Dunbar, who each helped me find quickly the source of an important quote from Saint Augustine.

•So many friends, especially Christian young adults, who have encouraged me by their enthusiastic interest in this topic and have waited excitedly to read what I have to say; I trust they will not be disappointed.

•My wife, Leisa, for her patience as I worked endless hours on my most challenging writing project since my doctoral dissertation.

•Last but not least, Saint Anthony, whom I called upon often to help this aging brain remember where to find something I had read. He never fails to assist me.

"Do You Know the Ordinances

of the Heavens?"

An Introduction to the Conversation

Then the Lord answered Job out of the whirlwind: … ‘Where were you … when the morning stars sang together, and all the sons of God shouted for joy? … Can you bind the chains of the Pleiades or loose the cords of Orion? … Can you guide the Bear with its children? Do you know the ordinances of the heavens?’

—Job 38:1, 7, 31, 33

MY MATERNAL GRANDPARENTS once farmed the humble red clay in a remote part of rural central Georgia. When I was young, they would host me for a weeklong visit from the city each summer. I still remember vividly, now more than half a century later, one moonless, wildly starry night when I walked outside the farmhouse to lie alone on the ground. There were no street lights, few artificial lights of any kind, allowing a spectacular view of the heavens rarely found these days.

For what seemed like hours, the twinkling of countless stars, the steady radiance of the planets, the immense shining path of the Milky Way, all captivated me and sparked my curiosity. I knew enough science even then to suppose that only angels could fly the astronomical distances between me and those heavenly bodies. And yet I dreamed …

What if I could travel to those shining worlds? What would I find there? Whom might I find there?

Suddenly the questions took an unsettling direction. What if they could travel to my world? Right here? Right now?

I ran back into the farmhouse and jumped in bed, eyes wide open all night.

An Ancient Debate

Of course, I was not at all alone in pondering such things. As we’ll see in the chapters to come, the possibility of intelligent life beyond earth has been debated since ancient times, both in Christian and in non-Christian cultures. (We will use a common shorthand term to refer to such life: the abbreviation ETI, for ExtraTerrestrial Intelligence.)

I was warned that certain segments of our contemporary society, particularly the academic world, might label me eccentric for writing about this topic. Yet those who hand out such labels must not be aware that in the light of history, such a dismissive attitude is itself revealed to be eccentric, an aberration, an anomaly. In fact, some of the best minds of the last twenty-five centuries in Western civilization—philosophers, theologians, scientists, literary figures—have energetically and sincerely engaged this subject.

To those who would award me a tinfoil hat, I simply reply that you will need many more such hats: for Democritus, Plato, and Aristotle; Origen, Athanasius, and Augustine; Albert, Aquinas, and Bonaventure; Copernicus, Galileo, and Kepler; Descartes and Pascal, Voltaire and Leibniz and Kant; Milton, Wordsworth, Tennyson, Dostoevsky; Thomas Paine, Benjamin Franklin, John Adams; and countless more.

Humility: Key to Wisdom

From the very outset of my study, I have been convinced that in this endeavor as in every endeavor, humility is the key to wisdom.

We need humility in making claims about what is scientifically possible. The history of science is one long story of surprising discoveries that reveal the limited vision of our assumptions about what can or cannot exist with regard to both natural phenomena and technology.

We need humility in making theological and philosophical claims about what is probable or fitting or other admittedly subjective designations, especially with regard to what God has done or might have done. For my thoughts are not your thoughts, neither are your ways my ways, says the Lord. For as the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts (Is 55:8–9).

We need humility in considering our place in this vast universe that God has created. Then Job answered the Lord: ‘Behold, I am of small account (Job 40:3–4). And for Catholics, if the Church’s Magisterium (teaching office) should make a definitive pronouncement about the subject of ETI, we need humility to accept what the Church will teach us.

God’s rebuke to Job so long ago rings down through the centuries to our own time: Do you know the ordinances of the heavens? (Job 38:33, emphasis added). Given the meaning of the Hebrew word translated here as ordinances, God is challenging us as he did Job: Do we know all the bounds, the laws, the measures, the decrees He Himself has appointed for the universe?

Quite simply, we do not. The Creator of the cosmos holds in His hands more mysteries than we can ever fathom.

What Difference Would It Make?

Some might ask, What difference would it make for Christians if we knew for sure that ETI exists? First, as the history of the ETI conversation demonstrates, Christians would hear the misguided claim from two types of ideological adversaries that extraterrestrial intelligence disproves their faith.

On the one hand would be those with a general skepticism toward religion, who would insist that the Christian (and especially the biblical) account of the universe cannot account for or accommodate the existence of nonhuman intelligent beings (other than angels). As we shall see, this is an unfounded claim that we have heard for centuries now.

On the other hand would be those religious (or, as they might prefer to say it, spiritual) souls who have rejected traditional Christian faith but still seek transcendent ideas and mystical experiences in various New Age or other occult spiritual traditions. Some such traditions have already incorporated messianic notions of ETI into their mythology, looking to our superior, more advanced space brothers (they go by many names) as the source of enlightenment and salvation for humankind. Such believers would welcome any disclosure of ETI existence as vindication of their beliefs—and proof that the Christian faith is false. Again, ETI proponents of this sort have been around for centuries, though they may be more numerous today.

The present work should put to rest the claims of both these groups that the public discovery or disclosure of ETI somehow disproves the Christian faith. Catholics and other Christians need not be disturbed by the possibility that intelligent extraterrestrial races could exist. As we shall see, though a public encounter with ETI would raise many questions to be answered about their spiritual and moral status, the Catholic faith could accommodate their existence as it has so many scientific discoveries over the centuries.

A second important consequence following a public, officially announced discovery or disclosure of the existence of extraterrestrial intelligence would be this: Some Catholics and other Christians, adopting for themselves the misguided notion that their faith is incompatible with the idea of extraterrestrial intelligence, would not deny their faith. Instead, they would deny the reality of ETI. To clarify, they would not deny that nonhuman intelligences exist and interact with humans; rather, they would conclude that all ETI experiences are actually deceptions perpetrated by demons.

As we will see, some claims of alien abduction or other interaction do seem to manifest the classical traits of demonic activity and deception. But it would be implausible to attribute (for example) retrieved alien spacecraft to demons who have no need of physical transport. In addition, there are countless reports of UFOs that seem to lack any demonic characteristics. The truth, Our Lord declared, will set us free (see Jn 8:32), so a false belief that any evidence of ETI is a demonic deception would ultimately bind and mislead us in important ways.

Other Reasons for Reflection

Still other reasons for reflecting on the possibility of ETI in light of the Christian faith become evident when we ponder seriously its many implications. First, the existence of ETI would demonstrate to us in new ways the greatness of God, the vastness of His wisdom and power, creativity and love. It would unveil one more rich meaning of the psalmist’s cry, The heavens are telling the glory of God; and the firmament proclaims his handiwork! (Ps 19:1).

Second, the knowledge of ETI could at once both humble us and exalt us: When I look at your heavens, the work of your fingers, the moon and the stars which you have established, what is man that you are mindful of him, or the son of man that you care for him? Yet you have made him little less than the angels, and you have crowned him with glory and honor (Ps 8:3–5).

We could learn humility if we were to discover that God has many other beloved sons and daughters across this vast cosmos. Meanwhile, it would reveal to us in a new and profound way how great is our dignity—not just because we have been made in the image of God, but also because He Himself has visited this tiny planet, one among billions, to become One of us and redeem us.

In scriptural studies, the ETI conversation raises important issues in the interpretation of certain biblical texts, and for Catholics, the interpretation of magisterial texts as well. Can we reasonably conclude that these texts are intended to address only the human situation on earth and in heaven, without having intended implications for intelligent life forms beyond human beings and angels?

In Christian theology, the issues raised have potential implications first of all for Christology—that is, our understanding of the person and work of Jesus Christ. How would ETI relate to the human incarnation of the eternal Son of God, the Second Person of the Blessed Trinity?

This question then leads to specific issues in soteriology—that is, our understanding of salvation. Could there be a race of ETI that has never fallen and needs no special divine act of redemption? On the other hand, if an ETI race is fallen, as we are, would God necessarily offer them redemption, and if so, how might He redeem them?

Issues in eschatology are raised here as well—that is, our understanding of the Last Things. What would be the ultimate destiny of ETI, and how would that destiny be related to our own destiny as human beings? What role would they play, what position would they occupy, in the final consummation of all things?

Finally, a discussion of alien natures inevitably has implications as well for Christian anthropology—that is, our understanding of what it means to be human, seen in the light of faith. The English word define has a Latin root that means to mark the limit of, to determine not only what something is but also what it is not. The existence of an intelligent species not descended from Adam on earth would press us to reflect more deeply on the Christian understanding of not only what it means to be human but also what it means to be fallen, and what it means to be redeemed. Learning more about creatures who are like us in certain ways but fundamentally different in others would be a path to better understanding of ourselves.

Questions and Issues to Address

A book on this topic could take the discussion in countless directions. In light of the concerns we have noted, we will seek to focus on addressing these questions:

•What have Catholic and other Christian thinkers throughout history had to say about the possibility of ETI?

•Which passages in Scripture and in the magisterial teaching of the Catholic Church might shed light on the topic?

•Are alleged human encounters with ETI simply a form of demonic deception and manipulation?

•Is belief in ETI compatible with the teaching of the Catholic Church?

•What would be the possibilities for the spiritual and moral status of an extraterrestrial intelligent race?

•What relationship might these possible forms of ETI have to Jesus Christ, His incarnation, His redemptive work, and His final appearance in glory as Lord and Judge?

•Would a public ETI discovery, disclosure, or encounter be a threat to the faith of Catholics, or would it have the potential to clarify and confirm our faith?

•How should the Church prepare for the possibility of public ETI discovery, disclosure, or encounter, and how should the Church respond to such an event?

•If we were to experience a public encounter with ETI, with an ongoing conversation, what relevant questions, with theological implications, would need to be answered about their nature, their moral status, and their intentions toward us?

Many Catholics and other Christians may never have considered these questions to be important. They may never have considered them at all. Yet they do have significant implications, as we have noted.

Scope and Approach

Some authors have examined the topic of Christian thought about ETI primarily as historians, without proposing theological conclusions. Others have approached the subject as Christian philosophers. Still others have engaged in lively theological debate but with scant reference to specific scriptural and doctrinal texts that have an important bearing on the topic for Christians and for Catholics in particular.¹

My academic training and experience are as an historical theologian and student of Scripture in the Catholic tradition. For this reason, my work will focus on the subject of ETI in light of Scripture, the teaching of the Catholic Church, and the debates among Christians and other thinkers throughout the history of the Church.

A number of theological studies have spent considerable time surveying the scientific debates related to extraterrestrial intelligence. These debates tend to focus on two concerns: The first is whether ETI is more likely to be common throughout the universe or extremely rare (perhaps even unique to planet Earth). The second is whether contact between multiple forms of ETI would be technologically possible, given the vast chasms of time and distance between habitable planets.

Though I have read deeply in the scientific literature with regard to extraterrestrial intelligence, I have decided not to spend much time discussing the scientific context in this book, for several reasons. First, I am not a scientist, and other writers have already done an admirable job of presenting the strengths and weaknesses of the opposing scientific positions. I recommend especially David Wilkinson’s Science, Religion, and the Search for Extraterrestrial Intelligence (Oxford University Press, 2013). Wilkinson holds a PhD in Theoretical Astrophysics as well as one in Systematic Theology, so he is immanently qualified to address these issues.

Second, the various scientific arguments proposed appear to me thoroughly speculative and the evidence inconclusive, given the uncertainties of the subject matter. So much of what we know, or think we know, about the fundamental nature of the cosmos and the laws of physics has been challenged in recent times, and basic scientific paradigms may be shifting, as they have in the past. We do well not to make theological arguments based on current scientific assumptions about what is or is not possible with regard to the existence of ETI. And we cannot simply rule out the possibility of interstellar travel as long as our knowledge of fundamental cosmology and physics is so limited.

In any case, my goal is not to make claims about the likelihood of ETI’s existence or the possibility of making contact with it. The primary concern of this book is to show that the Christian faith as traditionally held by the Catholic Church would not be contradicted by the public discovery or disclosure of extraterrestrial intelligence.

I do have opinions about what are popularly called UFOs or Unidentified Flying Objects. (The more current designation is UAP: Unidentified Aerial Phenomena.) But the historical and theological arguments I make here do not rest on the credibility of claims regarding such phenomena, nor even on the nature of what is being observed—whether they might actually be of extraterrestrial origin or might represent something more astounding. For this reason, I bring UAP into my analysis only when needed to explain an historically eccentric trait of our contemporary culture: the widespread failure to take the ETI issue seriously.

Even so, I consider UAP an important subject in its own right, and my guess is that most people who choose to read a book about ETI will reasonably expect that at least a few pages will be devoted to the topic. With this in mind, I have included an appendix entitled What About UFOs?

The public discovery or disclosure of extraterrestrial intelligence would of course raise questions about how best to interpret certain biblical passages and Church doctrines. But new scientific knowledge of this sort could be accommodated with integrity within the doctrinal and devotional framework of this ancient faith. For this reason, whichever scientific position on these matters turns out to be the true one (if we should find out this side of heaven), the Catholic Church can embrace the truth, and the Catholic faith will serve to illuminate and interpret what science or experience will teach.

One author to whom I owe a great deal (in the study of this subject as in so many others) is the celebrated and inimitable Christian writer C. S. Lewis. A Cambridge professor of Medieval and Renaissance English, he was formally trained neither as a scientist nor as a theologian. Yet he had much of value to say about this topic because of an acute clarity in analysis, a startlingly wide range of interests, a phenomenal breadth and depth of study, and a marvelously rich imagination.

In writing about ETI, Lewis tends to take one of two approaches, both appropriate for a popular rather than scholarly audience. In essays such as Religion and Rocketry, he reasons in prose at a simple, common-sense level. In novels such as Perelandra, he weaves a richly speculative tale that opens to the reader’s imagination a wide horizon of possibilities. In both approaches, he demonstrates a brilliant and exemplary humility. I trust that I have learned from him in crafting my approach.²

Curiosity and Wonder

My fervent hope is that this study can in some way make a contribution to the fascinating, age-old conversation about ETI and the Christian, specifically Catholic, faith. My goal is to embrace the attitude of inquiry once described by Alistair Cooke: Curiosity endows the people who have it with a generosity in argument and a serenity in their own mode of life which springs from their cheerful willingness to let life take the form it will—even, we might add, extraterrestrial life.³

If we are to have any chance at understanding these things, we must maintain a sense of wonder—an attitude of humility in the face of mystery. As usual, Shakespeare says it best. His title character in Hamlet sets the stage for our conversation when he tells Horatio: There are more things in heaven and Earth … than are dreamt of in your philosophy.⁴

Paul Thigpen, PhD

November 15, 2021

Feast of St. Albert the Great, OP

Theologian, philosopher, scientist, mediator

Patron saint of philosophers and scientists

Doctor of the Church

____________________

¹ For historical surveys and primary texts of the theological conversation about ETI, see Steven J. Dick, Plurality of Worlds: The Extraterrestrial Life Debate from Democritus to Kant (Cambridge: Cambridge University Press, 1982); Michael J. Crowe, The Extraterrestrial Life Debate, 1750–1900: The Idea of a Plurality of Worlds from Kant to Lowell (Cambridge: Cambridge University Press, 1986; new ed., Mineola, N.Y.: Dover Publications, 1999); Michael J. Crowe, ed., The Extraterrestrial Life Debate: Antiquity to 1915: A Source Book (Notre Dame, Ind.: University of Notre Dame Press, 2008); Steven J. Dick, The Biological Universe: The Twentieth-Century Extraterrestrial Life Debate and the Limits of Science (Cambridge: Cambridge University Press, 1996). For a Thomist philosophical approach, see Marie I. George, Christianity and Extraterrestrials? A Catholic Perspective (New York: iUniverse, 2005). For primarily theological discussions, see the works noted in later chapters of this work.

² Religion and Rocketry appears in C. S. Lewis, The World’s Last Night and Other Essays (New York: Harcourt Brace, 1952); Out of the Silent Planet, Perelandra, and That Hideous Strength are a trilogy of science fiction novels, now available together in a 2011 edition by Simon & Schuster.

³ Quoted in David Wilkinson, Science, Religion, and the Search for Extraterrestrial Intelligence (Oxford: Oxford University Press, 2013), 3.

⁴ Hamlet (1.5.167–8).

I

A History of the ETI Conversation

1

Worlds without Number

A Lively Debate since Ancient Times

With God it is easy to make worlds without number and end. As it is easy for you to conceive a city and worlds without bound, unto God it is easy to make them; or rather again, it is easier by far.

—Saint John Chrysostom¹

ARE WE ON Earth the lone intelligent inhabitants of this vast universe? The angels, both fallen and unfallen, act upon it without physical bodies in the fulfillment of their assigned missions, whether heavenly or infernal. But do we humans share the cosmos with any other embodied intelligent forms of life created by God?

Today, speculation about the existence of extraterrestrial intelligence (ETI) is livelier than ever. A growing number of science fiction novels and films about alien life continue to find a wide and enthusiastic audience. Scientists look for evidence of life beyond earth through multiple means: interplanetary explorations by NASA;² studying unidentified aerial phenomena (UAP) and searching beyond Earth for evidence of extraterrestrial technological artifacts (such as possible ETI space probes);³ monitoring electromagnetic radiations from the heavens for potential signs of transmissions from extraterrestrial civilizations;⁴ and transmitting interstellar messages in an attempt to contact such civilizations.⁵

Civil and military authorities in the United States and other nations have established formal agencies to examine continuing reports of UAP that cannot be explained by conventional, or even cutting-edge, technology. Elected officials are demanding more government transparency about these matters, with concerns about national security.

Meanwhile, stories of alien abductions or other close encounters have multiplied. Even new religious traditions have emerged, such as Scientology, whose novel mythologies claim to be based on revelations from or about ETI. Some have concluded that ancient pagan myths about the gods, and even biblical accounts of angelic beings, actually refer to creatures who visited Earth from other planets. Others now look for alien saviors to descend from the heavens, enlightening us and rescuing us from the miserable state we have created for ourselves on this planet. Many non-Christians insist that any public revelations of ETI would disprove the Christian faith.⁶

Even so, many who contribute to this intensifying interest in ETI fail to realize that such contemporary discussion is only the most recent portion of a debate that stretches back at least twenty-six centuries. How can we hope to come in on the tail of such a lengthy conversation and make a useful contribution if we have no idea what has already been said? To do justice to this complex topic, we must begin an exploration of ETI and the Catholic faith with an historical overview.

Though I am convinced that the historical aspect is essential for understanding our subject, I recognize that some readers may be less interested in history and more eager to read my theological analysis in light of that history. Those who find themselves in that category should proceed to the second section of the book, A Contribution to the ETI Conversation. They will nevertheless at times find themselves, I suspect, referring back to previous historical chapters for important background information.

Ancient Greek Debates

Fathers and Doctors of the Catholic Church, Catholic philosophers and theologians, popes and bishops, friars and priests, scientists and saints have all taken part in the ETI conversation. But the conceptual foundations for their discussion were laid in the centuries before Christ.

In the long history of Western thought, the earliest surviving records of debate with implications for ETI come from ancient Greek philosophers in the sixth, fifth, and fourth centuries bc. The question of intelligent life beyond earth was at that time part of a larger discussion about what came to be known as the plurality of worlds. This notion originally referred, not so much to multiple heavenly bodies in our universe (the stars, planets, their moons, and other features of the cosmos), but rather to multiple entire universes, all coexisting independently of one another, each cosmos with its own earth and celestial bodies.⁷

Thinkers in the Greek philosophical tradition known as atomism concluded that there is indeed a plurality of such worlds. They reached this conclusion on the basis of several assumptions about all that exists: First, all things come into existence, they taught, not by some action of the gods, but by the constant movement and coalition of particles they called atoms. Second, the laws of nature governing these atoms and their movement are universal. Third, there is nothing special about our planet Earth. Fourth, nature tends to realize all possibilities. What is potential eventually becomes actual.⁸

Some atomists, such as Leucippus (fifth century bc) and Democritus (d. 361 bc) insisted that these multiple worlds are innumerable. Epicurus (d. c. 270 bc) taught that there are infinite worlds both like and unlike this world of ours, and since all possibilities are realized, in all these worlds there are living creatures.⁹ Under the influence of these Greek philosophers, this plurality of worlds idea eventually gained a following among certain Roman thinkers as well, such as the poet Lucretius (99–55 bc).

Plato, Aristotle, Plutarch

Meanwhile, the celebrated Greek philosopher Plato (427–347 bc) taught that the universe was organized by the Demiurge. This figure was a kind of divine craftsman—not like the omnipotent God of the ancient Hebrews Who spoke the universe into existence out of nothing, but rather a universal architect and builder who organized eternally existing matter and brought order out of the chaos. The Demiurge, Plato insisted, distributed souls to the stars (the stars, he believed, were living creatures), inserting one soul into each star.¹⁰ In this way, he conceived of ETI in the form of living stars who moved across the sky.

Aristotle, Plato’s most famous pupil, rejected the atom-ist teaching that there could be more than one cosmos. The philosophical position he developed would become extremely influential in the medieval Christian world. His geocentric—that is, earth-centered—model of the universe led him to conclude that all things in existence have a single circumference and a single center, and that center is the Earth. For this reason, there is no possibility of another universe. Aristotle presented other arguments against plural universes as well, but this one was primary.

Aside from the debate over multiple worlds, with at least some of those worlds inhabited, a few Greek philosophers speculated about extraterrestrial life in a much closer setting: the Moon. Followers of the ancient sixth-century philosopher and mathematician Pythagoras claimed that the Moon was much like the Earth, with plants and animals and intelligent creatures vastly superior to humans. Rather than insisting on either an infinity of worlds or a single world, this speculation took a kind of middle ground: Within the single universe that we ourselves inhabit, the Moon is a second inhabited world, though not its