A Canticle for Leibowitz Walter M. Miller, Jr.'s A Canticle for Leibowitz treats religion very differently than does most science fiction. Miller's Brother Francis is charged with discovering the meaning of faith and God in the wake of total nuclear destruction. The particular religion extent in Miller's future is the venerable Catholic Church, an institution that has survived near-annihilation before.
The novel begins with the discovery of a tomb by a novice, Francis, a tomb that may or may not contain the remains and relics of his order's founder, Leibowitz. Miller thereby introduces questions in the reader's mind about the nature of what Francis has really found, what Leibowitz' soul was really like, and how strong Francis' faith remains. Faith is set apart from knowledge cleanly and clearly in this section.
The next section takes place 500 years later, when a scholar, Thon Taddeo, is trying to piece together the real story of what happened to civilization after the nuclear holocaust.
In sharp contrast to Francis' faith, Thon is filled with doubt which becomes his major way of approaching life and finding truths. History is revealed to be inconsistent and subject to interpretation and loss. History is not nearly as reliable as Francis' frail desert faith.
The last section of the novel shows the first Earth colonists arriving at Alpha Centauri. There is another nuclear explosion and the threat of another apocolypse, but the real question hinges upon suicide. Government sanctioned euthanasia has encroached upon the monastery of Leibowitz, both physically, in the form of a euthenasia station, and spiritually, as the abbot and a doctor spar over ethics and scripture.
As a whole, the view of history, faith, and "truth" depicted in A Canticle for Leibowitz is quite dark and thought-provoking without being preachy. Knowledge of the past is unreliable and unable to prevent the same problems from plaguing humanity for eons. The things that could save humanity are ridiculed and forgotten, but the book ends with a strange feeling of success. No matter how foolish and suicidal humanity is and will become, the species will survive. Faith in ourselves seems even more a part of us than faith in Francis' God. Haunted by the spectre of religion and resurrection, humanity learns what it takes to hold onto life against all odds.