Pope Francis has called for a church that is less strict and more compassionate towards "imperfect" Catholics, such as those who divorced and remarried, saying "no one can be condemned forever".
Francis said gays should be respected but firmly restated the church's position that there are "absolutely no grounds" to equate gay unions to heterosexual marriage.
In a 260-page treatise called "Amoris Laetitia," (The Joy of Love), one of the most eagerly awaited pronouncements of his pontificate, made his case for a more merciful and loving church.
The keenest anticipation centred on what he would say about the full re-integration into the church of Catholics who divorce and remarry in civil ceremonies.
Under current church teaching they cannot receive communion unless they abstain from sex with their new partner, because their first marriage is still valid in the eyes of the church and they are seen to be living in an adulterous state of sin.
"No one can be condemned forever, because that is not the logic of the Gospel! Here I am not speaking only of the divorced and remarried, but of everyone, in whatever situation they find themselves," the Pope said.
Presenting the document at a packed Vatican news conference, Cardinal Christoph Schoenborn of Vienna, called it "a classic case of the organic development of doctrine," which he described as being a continuation of theological thought without rupture with the past.
Progressives have proposed the use of an "internal forum" in which a priest or bishop work with a Catholic who has divorced and remarried to decide jointly, privately and on a case-by-case basis if he or she can be fully re-integrated and receive communion.
Francis seemed to embrace this view, saying he could "not provide a new set of general rules ... applicable to all cases", but he called for "responsible, personal and pastoral discernment of particular cases".
Father James Bretzke, professor of moral theology at Boston College, said while Francis did not explicitly give a green light for remarried Catholics to return to communion, "the dots are pretty close together, you can connect them reasonably easily and conclude that he is saying this is a possibility.
"If he's not opening the door, he is at least showing you where the key under the mat is."
Francis said he understood those conservatives who "prefer a more rigorous pastoral care which leaves no room for confusion" but the church should be more attentive to the good that can be found "in the midst of human weakness".
"The church turns with love to those who participate in her life in an imperfect manner," he said, including in this category those Catholics who are cohabiting, married civilly or are divorced and remarried.
Conservative American Catholic author George Weigel said he did not see an opening to the divorced and remarried but rather "a call for the church to be creative in integrating people in difficult situations".
Francis praised the "erotic dimension" of love within marriage and said the Church needed a "healthy dose of self-criticism" for in the past preaching that procreation was the "almost exclusive" reason for marriage.