During the past three decades, data from a number of sources have fueled a resurgence of interest among scientists in the possibility of extraterrestrial life. The previous high point (the 1960s) of activity in the search for extraterrestrial life focused on the possibility of intelligent extraterrestrial life forms. Ralph Stearley argues the present discussion is more informed and more modest in its scope, attempting to assess the probabilities of potentially habitable worlds elsewhere in the universe. The books under review in this article take several approaches to estimation of such probabilities. Diverse observations now support the contention that many potentially habitable worlds exist "out there." Whether such worlds actually host living creatures, or especially sentient life forms, is more problematic and contentious. How should Christians react to the data accumulated during the past 30 years? Can the Christian understanding of God's pleasure in created beings be extended to other planetary settings? Mr. Stearley is Professor of Geology at Calvin College.