As a confirmed atheist who has always had trouble understanding how some people can be religious but still believe in evolution, I approached this novel with trepidation, and was close to giving up on a couple of occasions. However, the brilliance of Blish's earlier entry in the SF Masterworks series - Cities in Flight, persuaded me to continue, and I have to say that I'm very glad I did. Some people would say that religion has no relevance to science, and it is an opinion that the priest Ruiz Sanchez hears a great deal throughout the novel. By giving the character the chance to defend himself throughout the story, I have started to understand one thing about science and religion - that a person's beliefs do not have to be at odds with their skills as a scientist. Ruiz Sanchez is a biologist who believes in God, and as he points out himself in the book, that belief is a constant whether he is praying on earth or praying on a distant planet. He has reconciled the theory of evolution with the theory of Adam and Eve, and sees his faith and his science as being irrevocably intertwined, to the point where he is prepared to face eternal damnation for his decision about Lithia. As for the ending of the book : I won't spoil it for those who haven't read it, but who can really say what is responsible - the science of man or the hand of God ? A perturbing book but fabulously insightful, both for those with faith and those without.