VATICAN CITY (TheBlaze/AP) — Pope Francis issued his first encyclical Friday, a meditation on faith that is unique because it was written with someone else: Benedict XVI. In the document, though, Francis also drives home the point that marriage is an institution, at least under Catholic doctrine, that is exclusive to a man and woman.

Benedict’s hand is evident throughout much of the first three chapters of “The Light of Faith,” with his theological style, concerns and reference points clear.

Francis’ priorities come through strongest in the final chapter, where the Argentine Jesuit insists on the role of faith in serving the common good and giving hope to those who suffer. It includes his first clear statement as pope on marriage being a union between man and woman with the aim of creating children.

Pope Francis Affirms: Marriage Is an Institution Between One Man and One Woman

In this photo provided by the Vatican newspaper L’Osservatore Romano, Pope emeritus Benedict XVI, left, is welcomed by Pope Francis during a ceremony for the unveiling of San Michele Arcangelo statue at the Vatican, Friday, July 5, 2013.  (AP)

“This union is born of their love, as a sign and presence of God’s own love, and of the acknowledge and acceptance of the goodness of sexual differentiation, whereby spouses can become one flesh and are enabled to give birth to a new life,” the encyclical reads.

Francis also cites his namesake, St. Francis of Assisi, as well as Mother Teresa, in saying “How many men and women of faith have found mediators of light in those who suffer!” And he concludes with a prayer to Mary, to whom he is particularly devoted.

The encyclical didn’t appear to break any new ground in church teaching; its novelty was entirely in the dual authorship, signed and unsigned, and that it was the first of Francis’ nascent pontificate.

Francis acknowledged in the introduction that he merely “added a few contributions of my own” to Benedict’s “fine” first draft, which the German theologian left unfinished when he retired in February. Together, the two popes crafted the final installment of Benedict’s conceived trio of encyclicals on the three Christian theological virtues: charity, hope and faith.

Francis, however, gets publishing rights and he alone signed the short, 82-page encyclical, which is the most authoritative teaching document a pope can issue. It was signed on June 29, the feast of Saints Peter and Paul, a feast day important for the unity of the church that was perhaps appropriate given the document’s combined authorship by the two successors of Peter.

And as if to underscore the shared message, Francis and Benedict were together Friday morning for the inauguration of a new monument inside the Vatican gardens — the first time they have been seen together since May 2, when Francis welcomed Benedict back to the Vatican after his initial retirement getaway.

Pope Francis Affirms: Marriage Is an Institution Between One Man and One Woman

Pope Francis poses with Italy’s Prime Minister Enrico Letta during a private audience at the Vatican, Thursday, July 4, 2013. (AP)

The two men in white embraced one another, and both sat on chairs in front of the monument for the duration of the ceremony.

At a press conference launching the document, Vatican officials took pains to stress that this was Francis’ encyclical, even though it contained issues dear to Benedict, was drafted by him and completed a triptych that he set out to write at the start of his pontificate.

“The pope is Francis,” said Archbishop Gerhard Mueller, the head of the Vatican’s doctrine office. “It’s not signed by two popes because we only have one pope.”

Archbishop Rino Fisichella, head of the Vatican’s evangelization office, said Francis’ style, citations and “peculiarities” come through and represent “a true introduction to his magisterium and allow us to understand better the pastoral style that distinguishes him.”

In the document, the two popes go back to the Old Testament for the origins of the Christian faith in God and then explore one of the major concerns of Benedict’s papacy, the interplay of faith and reason and the dangers of relativizing truth.

“In contemporary culture, we often tend to consider the only real truth to be that of technology: truth is what we succeed in building and measuring by our scientific know-how, truth is what works and what makes life easier and more comfortable,” they write, rejecting that view.

By the final chapter, the discussion comes around to more tangible concerns, the need for Christian faith to be at the service of justice, law and peace, and for the family to be at the forefront of imparting the faith to the young. These are clear concerns to Francis, who heads to Brazil in a few weeks for the church’s youth fest, World Youth Day.

“Faith is not a light which scatters all our darkness, but a lamp which guides our steps in the night and suffices for the journey,” he writes. “To those who suffer, God does not provide arguments which explain everything; rather his response is that of an accompanying presence, a history of goodness which touches every story of suffering and opens up a ray of light.”