By Justin McLellan, Catholic News Service

VATICAN CITY (CNS) — Humanity needs a revolution in how it thinks about sex, Pope Francis said.

“We need to discover the beauty of human sexuality by once again turning to the great book of nature, learning to respect the value of the body and the generation of life, with a view to authentic experiences of conjugal love,” he wrote in a message to participants in an academic conference on fertility published April 28.

The pope said that serious education in the relational and procreative dimensions of sexual relationships is increasingly necessary “in a world dominated by a relativistic and trivialized view of human sexuality.”

Such education requires “an anthropological and ethical approach in which doctrinal issues are explored without undue simplifications or inflexible conclusions,” he wrote.

Pope Francis underscored the need to affirm both the unitive and procreative elements of sex, noting that without them “the experience of sexuality is impoverished, reduced to sensations that soon become self-referential, and its dimensions of humanity and responsibility are lost.”

“The tragedy of violence between sexual partners — including the murder of women — here finds one of its main causes,” he added.

The fertility conference, hosted at Rome’s Catholic University of the Sacred Heart, marks 70 years since the development of the Billings Ovulation Method of natural family planning, which attempts to identify fertility patterns to avoid or achieve conception.

While this approach may have appeared “outdated and less reliable” when compared with artificial birth control, the pope said, the Billings method “has continued to prove timely and challenging,” since it has led to serious reflection on creating an integral vision of human sexuality and promoting “a culture that welcomes life.”

Pope Francis said the Billings method and others like it offer resources for responding to difficulties with conceiving by helping spouses identify their most fertile periods.

While the pope supported using scientific methods that can enhance fertility to assist and support a legitimate desire to conceive, he said that in vitro fertilization, to “suppress” embryos, the buying and selling of sperm or eggs and to resort to surrogate parenthood are “wrong.”

“The ideological and practical separation of the sexual relationship from its generative potential has resulted in the quest for alternative forms of having a child, no longer through marital relationships but through the use of artificial processes,” he wrote.

Pope Francis said that such an “imbalance in the view of sexuality,” along with various social and cultural factors, is “at the root of the current demographic crisis.”

The pope also emphasized the role of Catholic universities to further study fertility and spread awareness of fertility and natural family planning methods.

“Promoting knowledge of fertility and natural methods also has great pastoral value,” he wrote, “since it helps couples to be more conscious of their marital vocation and to bear witness to the Gospel values of human sexuality.”