What are the motifs in A Canticle for Leibowitz by Walter M. Miller, Jr.?

Moral Responsibility is a recurring idea in the story. A Canticle for Leibowitz examines two interrelated moral questions of warfare and the right to life. The first generation of nuclear scientists, Leibowitz's colleagues, are granted the benefit of the doubt. They may not have known their work would lead to the Flame Deluge and create generations of genetic mutants. Over widespread objections, including some Catholic thinkers, the Pope insists any human conception must be allowed to come to term and the offspring, however deformed physically or mentally, must be cared for and brought to maturity.