The Size of the Cosmos as an Existentiell and Theological Problem
A further question that must be touched upon in this discussion pertains to the size of the cosmos as understood by natural science today. While it is true that in this question there is not even the semblance of a direct contradiction between the affirmations of natural science and those of traditional theology, since neither of them have put forth statements about the size of the universe, the question does contain, nonetheless, a difficulty of considerable proportions.
Being Lost in the Cosmos as the Expression and Mediation of an Ultimate Experience of Contingency
For at least as long as the geocentric view of the world prevailed, the cosmos was in the naive experience of Christians their dwelling place. Created by God for them and for their history of salvation, they could see its contours. It was built for them and it was there for them. True, the earlier idea of the cosmos as the determining factor of their religious experience was not structured in a unified way. For example, it was not easy to fit angels into it. On the one hand, being pure spirits, they could not quite be accommodated in this edifice and yet, on the other hand, they were supposed to dwell in one of the heavenly spheres. But when Suarez, for example, was still trying to fit the "ascension of Christ" to the caelum empyreum into the ancient cosmos even to the point of asking the question whether the ascended Christ was dwelling in the uppermost sphere of heaven or over it, then we can see how closely the ancient view of the world was amalgamated with Christian dogmas, extending even to the idea of a connection between the fires of hell and known volcanoes.
Nowadays the Christian has to live on a tiny planet in a solar system which in its turn is part of a galaxy of a hundred thousand light years with thirty billion stars and whereby this galaxy is estimated to be only one of a billion such galaxies in the universe. In such a universe it is certainly not easy for human beings to feel that they are the ones for whom this cosmos ultimately exists. In a cosmos of proportions so tremendous that they even defy the power of the imagination, it is quite possible for human beings to feel that they are an accidental, marginal phenomenon, particularly when they know themselves to be the product of an evolution which itself has to work with numerous and improbable accidents. Under this aspect people accustomed to think in the categories of natural science will experience a further feeling of existentiell dizziness if they are then expected to realize that the eternal Logos of God who moves these billion galaxies is supposed to have become man on this tiny planet which, like a grain of sand, exists somewhere or other in this universe.
This feeling of dizziness, repressed of course, because of the narrow horizon of everyday life, cannot be kept away by sublime reflections on time and space on the part of modern physics, which undeniably is becoming more and more abstract. The question remains whether and how ordinary Christians and ordinary people in everyday life can gradually get used to being lost this way in the cosmos. What people believe about themselves, their destiny and their worth will not turn out to be deceptive because of their vulnerability in this vast cosmos (theological reasons are still at least as good as those of modern physics, even if both require different ultimate positions in order to achieve existentiell realization). The question is simply how both views of the world can coexist in the same consciousness without the one or the other to mutual disadvantage consuming people's existentiell strength for itself alone. First of all, one will simply have to accept this situation and live with it, especially since people who perceive things in a scientific way (even outside of Christianity) in the existentiell decisions of their lives also take themselves with a greater seriousness–and this rightly and unavoidably– than would seem to be warranted when they consider their cosmic insignificance.
Today, and more than ever in the future, human beings and Christians are also going to have to realize more clearly and more radically that their very recognition and acceptance of the fact of being lost in the cosmos actually raises them above it and enables them to realize it as an expression and a mediation of that ultimate experience of contingency which they, in virtue of their ancient faith, must perceive and accept before the infinite God as finite creatures. In this light one is justified in saying that the cosmos has become "more theological" for humankind, which is to say that it points more inexorably than before to the experience and acceptance of the fact of being created. In this way the feeling of cosmic dizziness can be understood as an element in the development of people's theological consciousness. If people's scientific consciousness today proceeds from the obvious assumption (although this assumption is not so obvious at all) that the scientific investigation of the cosmos can never come to an end, and if this conviction is a theological datum based on the fundamental incomprehensibility of God, then this experience that the universe is in a way immeasurable is, to a certain extent, nothing other than the spatial counterpart to the theological datum, and it is something that might be expected (after the fact, of course). If people have to give up their feeling of being at home in the universe in exchange for a feeling of not being at home, which reflects the character of their religious experience, then this is at root a legitimate element of humankind's fate. When, in addition, modern physics undertakes at the same time to calculate the finite extent of the actual universe, it is thereby once again documenting the peculiarity of the spirit in contrast to matter, which can reflect upon itself and its world, and then again place its world over against itself. In this way people can perceive the created finiteness of the world, despite its immeasurability.
A History of "Spirit'' on Another Star?
In this context we cannot entirely neglect a question which is again laying claim to our attention, although it is not entirely new. Is it conceivable that on other "stars" there are creatures consisting of body and soul equal or similar to human beings? The modern natural sciences will ultimately not be able to give any answer to the question of the fact. As far as the concrete possibility is concerned an answer is hardly to be expected either, since the probability, given the enormous number of stars, and the difficulty of the development of life up to the point where the "human being" emerges can hardly be factored out together. Still it must be said that in contrast to the ancient view of the world the fundamental possibility of a development of life to the point of intelligent consciousness can today no longer be excluded. This holds true especially because it would be an anthropomorphic idea that God the creator would bring the cosmic development at some other point so far that the direct possibility of conscious life would be present, but that then he would arbitrarily break off this development.
One should also note that traditional angelogy points to the fact that theological tradition also reckons with the coexistence of other personal creatures along with human beings. In this context a number of theological problems have emerged even prior to our problem (a common vocation to the same final goal; Christ as head of all creation, etc.).
Should one wish to speculate further on this existentielly rather remote problem, one might say that it would make sense to ascribe to these creatures of body and spirit a supernatural destiny immediately directed to God (notwithstanding the gratuity of grace), but that we, of course, can discern nothing about the presumable history of freedom of these creatures. In view of the immutability of God in himself and the identity of the Logos with God, it cannot be proved that a multiple incarnation in different histories of salvation is absolutely unthinkable.
Our only purpose in bringing all these things up is to show that theology need not put any absolute veto on the idea of history of "spirit" on another star. Theologians will not be able to say anything further on this question. They will point to the fact that the purpose of Christian revelation is the salvation of humankind, not to provide an answer to questions which really have no important bearing on the realization of this salvation in freedom.
K. Rahner, Theological Investigations, vol. 21 (Darton: Longman&Todd, 1988), pp. 48-52.