The authors explain how believing and reasoning are two human activities that may be integrated to form a complete view of human existence. They take their title from the opening of John Paul II's encyclical Fides et Ratio, which speaks of the human spirit rising on the two wings of faith and reason to stretch toward the truth that is available to all.

In the first part of the book, the authors offer a basic encounter with traditional arguments for and against God's existence. They grapple with doubts arising from the question of evil and the discoveries of contemporary natural science. The final chapters take up questions from ethics and politics that impact the way individuals and communities choose to structure their lives.