Saint John Paul II's teaching on love and sexuality shows the dignity of the human body and how concrete acts of mercy are demanded of all of us, says priest and author Father Michael Gaitley.

"The heart of the Theology of the Body for me," said Fr. Gaitley, "is the idea that the body matters," and that "all of us are called in our bodies to reflect the self-giving love which is at the heart of the Trinity – which means putting mercy into action."

Fr. Gaitley is the director of the Association for Marian Helpers and spoke July 10 at the Theology of the Body Congress in Philadelphia. His comments addressed the relationship between Vatican II and Pope John Paul II's teaching on marital love and the family.

The teaching, unofficially termed the "Theology of the Body," was a series of over 100 talks on human love, sexuality, and the family delivered by Pope John Paul II between 1979 and 1984. Its relationship to Vatican II, Fr. Gaitley explained, was that both taught that faith is meant to be put into action through concrete, personal acts of faith and love.

As Archbishop of Krakow, Karol Wojtyla implemented Vatican II by promoting the "enrichment of faith," small communities of believers who took the teachings of the council home and had small-group discussions, carrying the truths from the head to the heart.

This knowledge of the heart "anticipates" the Theology of the Body, Fr. Gaitley explained. "We are the kind of beings that can take truths into our minds but then as we bring them into our hearts, the Word becomes flesh in us," he said.

"We become, in a certain sense, other incarnations of the Word, which is sort of an anticipation of Theology of the Body, that we are these amazing beings that can take just these ideas but then make them flesh in our lives so that people can see us as living Gospels," he added.

And the most important way to do this, he added, is to put "mercy into action."

"I would suggest to you that the most important truth that needs to go from our heads to our hearts to our lives is the truth that God is mercy. The truth that God is love. The truth that God is merciful love."

Fr. Gaitley gave five pillars of the Divine Mercy devotion: celebrating the Feast of Divine Mercy, venerating the image of Divine Mercy, praying the Divine Mercy novena, praying the Chaplet of Divine Mercy, and commemorating the Hour of Mercy each day at 3 p.m. These are all concrete ways of carrying the message of Divine Mercy from our head to our hearts, he maintained.

"But the last and most important part for the message of divine mercy is that we all have to put mercy into action," he added. "Deeds of mercy. Jesus told Faustina 'I demand from you deeds of mercy.'"

The priest then referenced Philadelphia archbishop Charles Chaput's remarks to the National Catholic Reporter in 2011, when he said: "If we don't love the poor, and do all we can to improve their lot, we're going to go to Hell. It's very clear from the gospels that we have the duty to do that."

As beings with both a soul and a body, we have to make "visible" the love of the Trinity in deeds of mercy, Fr. Gaitley emphasized.

"And part of the vocation of the human being is we're not spirits like the angels, we're embodied spirits, is that we're to make visible the invisible reality of God, in families, making visible the invisible reality of the Trinity, in the self-giving love that's fruitful."