The vastness of the universe and the recent discovery of planets point to the probability of intelligent extraterrestrials. Since 1995 -- less than 20 years ago -- more than 750 planets have been discovered outside of our solar system. New telescopes in the United States as well as around the globe are searching for life on what are now called "exoplanets." There are billions of suns in one galaxy, and recently astronomers concluded there may be five times as many stars in the universe as had previously been thought. With so many galaxies, each with billions of suns, it is likely that there are other civilizations.
Some years ago a group of scientists produced an exercise in probability: the Drake equation. It looks at the percentage of galaxies with the right kinds of stars, the percentage of stars forming planets, the percentage of planets hospitable to life, to intelligence, and to intelligence adequate to communicate out into space. Some scientists then estimate the number of intelligent civilizations just in the Milky Way to be between one thousand and one million.
A theologian would not presume to decide whether there are other intelligent beings in the universe. Does the Christian faith insist that only one salvation-history exists, that on Earth? The one recorded in the Bible? Is Jesus so central a figure that only he and his Middle Eastern religious world can reveal God?
To be involved with the divine, a being needs to be intelligent and free, an intelligent being in our material universe owning some form of body, some matter, some corporeality. They are not spirits traditionally called "angels." There might be countless forms of animal and vegetable life in the universe: "extraterrestrial" refers to those with mind and freedom.
A Christian approach to this possibility begins with the themes basic to the Christian faith (and to most religions): the knowing person, the person's relationship to God, sin and evil. In light of the vast universe, what does Christian faith tell us of God? Is God generous or stingy? Powerful or limited? What would a wider universe say about a godly God? Christian theologians tend to see God as free and limitless. Generosity moves God to have special contact with other beings, and Thomas Aquinas wrote that God is "most generous to the highest degree." Love carries the divine plans into external realizations, cosmos and human beings and their destinies.
What is most basic in religion is some contact by God within and yet beyond the forms of nature, a presence of what religion calls "revelation," "grace" or "salvation." Does this or that intelligent creature receive some special life and information from God? The ways in which supernatural life touches sensate intellect and will, the modes of contact in revelation may be quite diverse. It is a mistake to think that our understanding of "covenant," the "reign of God" or "redemption" exhausts the modes by which divine power shares something of its life. Distant creatures might be without grace and revelation, and they might be without evil, suffering and sin.
Toward kinds and degrees of evil, too, we must have an open mind. Evil does not exist necessarily, and, if it exists elsewhere, it might be of various kinds. The actions and contagion of sin, as we see in daily life and learn from the Bible, can have an individual and a collective form. Another race, however, might be free of both.
Does faith in Jesus cast doubt on other galactic races? Christians believe that Jesus is a human being with a special presence of the Word God. Incarnation involves one creature as the object of that one special divine relationship: it hardly presents all that God can do and is doing. Is not incarnation a cosmic form of divine love? Can there not be other incarnations? The power of a divine person is infinite and cannot be limited to anything created. Could the Word of God could be incarnate in creatures other than Jesus of Nazareth?
In past centuries a few theologians have pondered this topic. Origen in the third century saw the biblical life and work of Jesus in a dynamic cosmic framework where the Word of God moved through spheres of other intelligences becoming like them. A Franciscan university professor Guillaume de Vaurouillon taught in the 15th century that God could create an infinite number of worlds. Other planets would not have contracted sin just as their humanity is not from Adam, and Jesus would not travel to alien worlds to reveal to them. In the late 20th century Karl Rahner advised a theological openness about persons on distant worlds. He thought that Christian revelation's assertion of God's power, plurality and incarnation supported seeing goodness and intelligence throughout the cosmos.
Christian revelation has as its goal the salvation of the human race. And yet, Christianity suggests not a terrestrial elite behaving itself before a strict God but a universe aiming successfully at intelligence and at the presence of forms of divine love. The universe and its source invite these reflections. Religious faith encourages rather than fears reflection on our universe.