For thousands of years, human theology has been wrestling with the basic questions: Who are we? Why are we here? What is our connection to the Creator? These issues have been examined in a single, deep context: the belief that life on Earth is the only life in the universe. The finding of extraterrestrial life, even microbial in form, would irretrievably destroy that assumption. While scientists would celebrate such a discovery as a breakthrough in our understanding of biology, theologians and religious believers would face a monumental challenge. The confirmation of life beyond Earth would not necessarily disprove God, but it would force a radical and unprecedented expansion of theological thought, stretching ancient scriptures and doctrines to accommodate a cosmos teeming with life.
The most direct challenge would be to the idea of human uniqueness. Most religious traditions, more or less explicitly, situate humankind at the center of God's design. Within the Abrahamic religions—Judaism, Christianity, and Islam—the Genesis account of creation tells of God creating the Earth and its creatures, climaxing in man, created "in His image." The whole salvation drama, from the Fall to the salvation brought by Jesus Christ in Christianity, revolves around man. The finding of extraterrestrial life would pose fundamental questions. Are we, on our tiny planet, the only object of a universe-encompassing Creator's desire? If there is life out there, are those aliens also created "in God's image"? Do they have the same nature? Being special, being the favorite children of God, is a tenet of many religions. Discovering that we are not alone can be seen as a demotion, a humbling experience that we are only one among many creations within a grand cosmic tapestry. This would entail a major realignment from anthropocentric (human-centered) theology to cosmocentric theology.
Christianity has very profound implications, centered around the person of Jesus Christ. Christian theology is based on the premise that the Son of God became incarnate in human form to bring salvation from sin through death and resurrection. This is seen as a singular, once-for-all action for the entire human race. What if, though, there are other intelligent races? Would they then have their own nature, their own relationship with God? Centuries of theologians have considered this question. Would God neglect these other children? Would the Incarnation be replicated in a thousand worlds, with a thousand different Christs assuming extraterrestrial form? This idea, referred to as the "Multiple Incarnations" theory, is hard to accept for many since it would appear to downgrade the specificity of the Christ event on Earth. Alternatively, maybe the redemption available here on Earth is good enough for the whole universe, an idea that seems peculiarly Earth-bound. Or, maybe these other creatures never sinned and exist in a state of original innocence, a scenario that would destabilize the Christian concept of the universality of sin and the need for the Cross. There are no simple solutions to this within mainstream doctrine.
The find would also compel a re-evaluation of holy books. Scriptures were authored by men, for men, in a particular historical and cultural environment. They speak of God's relationship with man, not with such hypothetical creatures in Tau Ceti. They say nothing about extraterrestrials. Would the faithful interpret this silence as proof that aliens don't exist, or would they interpret it in some novel way, reading the text symbolically to make space for a larger creation? Some would say that lines such as "the heavens declare the glory of God" were always indications of something larger. Others would regard the discovery as a challenge of faith, needing to balance new learning with old wisdom. Fundamentalism, which is based on a literal reading of scripture, would be in a particularly severe crisis. More liberal theological traditions, which have already integrated modern science and historical criticism, may be able to find it simpler to accommodate, seeing the discovery as a wonderful display of God's limitless creativity.
The character of the life found would completely redefine the theological reaction. The discovery of unelaborate, microbial life on Mars or Europa would be monumental, but its religious implications would be less profound. It would indicate that the mechanism of the origin of life is not a miraculous accident exclusive to Earth, but an organic process in a universe designed to be productive. This would be naturally incorporated into most theologies as proof of a very creative and life-producing God. The universe would no longer be thought of as an empty, cold void, but as a garden with the seeds of life floating about. Most theologians would embrace this as proof that God's creative power permeates throughout the universe.
The finding of intelligent extraterrestrial life would be revolutionary, though. Contact with intelligent beings of similar or greater intellect would create questions of souls, salvation, and ethics. Do these intelligent beings have souls? If they do, are they provided salvation? How do they interact with the divine? Have they been given revelation? Do they possess their own prophets, their own scriptures, their own concept of God? The potential for a comparative cosmic theology is staggering. It may show that there are many ways to the divine, or it may show a single truth communicated in various forms throughout the galaxy. It might even show that these creatures have no such idea of God whatsoever, which would disprove the theory that sentient creatures are born with an awareness of the divine.
Certain religious beliefs may be more compatible with the idea of alien life than others. Buddhism and Hinduism, with their extensive cosmic cycles, many universes, and an infinite number of divine creatures (devas), already have a conceptual system that can readily fit a filled-up cosmos. Within these paradigms, the universe is already filled with various forms of conscious existence in different levels of spiritual growth. Mankind is but one step in a long series. Alien discovery would only substantiate what their cosmology has been implying for a long time. Likewise, Deism that holds to a distant Creator who initiated the universe on the basis of natural laws would not be impeded greatly. A Deist could reason that a God who created a law-governed universe would surely seed it with life.
Ultimately, finding alien life would be the final test of theological flexibility. Religions are dynamic; they have developed over the course of history due to new information, from the Copernican revolution that removed Earth from the universe's center to Darwin's theory of evolution. Finding extraterrestrials would be the next big challenge. In order for faith to be relevant, it would have to widen its conception of God from a tribal god that has a special interest in one species on one planet to a cosmic Creator whose imagination, love, and creative energy are as boundless as the universe itself. This would not be the death of God, but the birth of more magnificent, more glorious theology. It would encourage believers to view their religion as not a little, completed house, but as a living, developing organism, able to encompass a universe full of marvels that they had never before ventured to dream of. The finding would humble us, but it could also lead to a faith deeper and more wondrous than any heretofore known.