Critics and reviewers have busied themselves in listing the various themes which lend substance and depth to [A Canticle for Leibowitz]. Stanley J. Rowland (The Christian Century, May 1960) [see excerpt above] has noted the thematic treatment of the issue of euthanasia and of the conflict between church (spiritual) and state (temporal) authority. Edward Ducharme (English Journal, November 1966) [see excerpt above] has claimed that "Miller's narrative continually returns to the conflicts between the scientist's search for truth and the state's power." To this list I would add that Miller also examines the occasional clash between scientific speculation and religious doctrine.

No one can deny that these are important concerns in the novel, but considerations of structure preclude that any of these issues could serve as the major theme…. A major theme should give unity and direction to the entire work, and none of the themes already mentioned satisfies this...