The encyclical focuses its theme on faith, and completes what his predecessor Pope Benedict XVI had previously written about charity and hope, the other two theological virtues, in his encyclicals Deus caritas est and Spe Salvi. Francis took, in fact, the work of Benedict, who before his resignation of the papacy had completed a first draft of the text, to which the new pope made additions. Francis explicitly expresses in paragraph 7 of the encyclical: "These considerations on faith — in continuity with all that the Church's magisterium has pronounced on this theological virtue — are meant to supplement what Benedict XVI had written in his encyclical letters on charity and hope. He himself had almost completed a first draft of an encyclical on faith. For this I am deeply grateful to him, and as his brother in Christ I have taken up his fine work and added a few contributions of my own."
The text presents faith as a light that dispels the darkness and illuminates the way the human being is. It is divided into four chapters, to which are added an introduction and a conclusion. The encyclical traces the history of the faith of the Church (from the call of God to Abraham and the people of Israel, to the resurrection of Jesus), discusses the relationship between reason and faith, the Church's role in the transmission of the faith, and the role faith plays in the building of societies in search of the common good. The text concludes with a prayer to the Virgin Mary, who is presented as a model of faith.