Five hundred years after Galileo, our understanding of the cosmos continues to evolve in spectacle, from Einstein's theories of relativity to the recent discoveries in cosmic microwave background radiation (CMB), the light detectable to a mere 380,000 years after the Big Bang. Most of Christian theology, however, has been done as though there had been no Copernican Revolution, as though planet Earth and its inhabitants were still the center of the universe, with God primarily concerned with human well-being. Thomas O'Meara notes that theology has not kept pace with advancements in cosmology, and considers the divine from the standpoint of the wider cosmos—beyond Earth as the singular beneficiary of divine revelation. While timely and innovative, his procedure is not methodologically unusual; O'Meara follows traditional theological steps (employing Scripture, Origen, Aquinas, and both Protestant and Catholic thinkers through the twentieth century) when asking questions about the possibility of divine revelation to intelligent life in distant worlds. Rather than give a comprehensive overview of the subject or draw definitive conclusions, however, O'Meara's intent is to encourage a particularly Catholic treatment of what Ted Peters calls the “exotheological” perspective.

In this sense, Vast Universe is written in the clear, concise, and accessible style that characterizes of all of O'Meara's work. Here it is suitable for upper-division undergraduates. Nearing eighty, O'Meara has a certain freedom to ruminate about how intelligent life on other planets might compare to angels, or inquire whether the incarnation of the second divine person could be limited only to Jesus of Nazareth. As to the latter, O'Meara considers that the uniqueness of divine incarnation on Earth does not preclude the possibility of other incarnations in other life-forms that would be receptive to divine self-communication. O'Meara supports this assertion with Aquinas’ citation of Augustine with regard to widening the scope of divine freedom: “Christian doctrine does not teach that God was so joined to human flesh as to lose or resign control over the universe as though constricted by a baby” (48 n. 14).

Raising the issue of an extraterrestrial incarnation thus leads to the possibility that even the Word's terrestrial incarnation may not be exclusive to Jesus. That there may be other forms of intelligent life in other worlds leads O'Meara to question whether these worlds experience evil, sin, and grace as Christians understand these on Earth, which reflects back to the question of whether the terrestrial savior's horrific death was necessary for salvation. As with any experimental outlook, the where-may-it-lead of these issues may be disturbing for some, and exciting and refreshing for others. O'Meara shows that the great minds of Catholic theological history were unafraid to pose problems even if they did not endeavor to solve them. The point is to avoid the narrowness of perspective that ignores something as basic to science as the Copernican Revolution. Examining the complexity and vastness of the universe from the discipline of theology requires a willingness to appreciate the paucity of theological assertions that limit the activity of the divine.