 A Canticle for Leibowitz 's circular structure – and the cyclical history it presents – support a number of thematic and structural elements which unify its three sections . Although the novel 's events take place in a fictional future , the three parts allegorically represent crucial phases of Western history . The first section , " Fiat Homo " , depicts a Church preserving civilization , a counterpart to the " Age of Faith " after the Fall of Rome . The action of the second part , " Fiat Lux " , focuses on a renaissance of " secular learning " , echoing the " divergences of Church and State and of science and faith " . " Fiat Voluntas Tua " , the final part , is the analog of contemporary civilization , with its " technological marvels , its obsessions with material , worldly power , and its accelerating neglect of faith and the spirit . " 
