Asked about her expectations of the synod Pope Francis will open Oct. 4, Sister Nathalie said "that we listen to the Holy Spirit, we discern together, and we learn more and more as a church, really to be a church of brothers and sisters in Christ," all through the reception of the Second Vatican Council.

In 2021, Pope Francis named the 54-year-old French sister of the Congregation of Xavières the first female undersecretary in the Vatican's Synod of Bishops office. Since then, she has taken a multitude of flights across the globe to listen to synod participants.

"I like to quote a theologian from Australia, Father Ormond Rush. He says that synodality is the Second Vatican Council in a nutshell. So this synod is a call to continue the reception of the Second Vatican Council," Sister Nathalie told OSV News.

"We have discerned that synodality is the path for the church in the third millennium. It's the call of God for the church today in this context, in this time of history," she said.

"My profound desire is that we answer the call of God, and we discern the concrete way to become a more and more synodal church, because that's the call of God for the church today: to be more a missionary church and to continue to transmit the faith. Today we need to have this synodal style," she stressed.

She pointed especially to young people who became important protagonists of the synodal path, the two-year process leading up to the synod's general meeting, which will be held in two parts, in October 2023 and October 2024.

"My expectation is that we continue personally and together (on) a path of conversion and a path of really listening to each other, to listen to the Holy Spirit also, in a very prayerful way," she said.

On Sept. 30, Pope Francis will preside at an ecumenical prayer service with leaders from different Christian denominations joining him in prayer "in order to entrust together to the Holy Spirit the work of the 16th Ordinary General Assembly of the Synod of the Catholic Church."

The service will be in St. Peter's Square with Ecumenical Patriarch Bartholomew of Constantinople and Archbishop Justin Welby of Canterbury among faith leaders in attendance, along with thousands of other Christians, the Vatican said Sept. 25.

Following the ecumenical prayer service, the synod's delegates will begin a three-day retreat outside of Rome to prepare for the synod.

Asked about the attitude of delegates, who are from different parts of the world and may be from regions where local churches express disagreement, the synod undersecretary said she hopes "that every synod member could really come to the synod with an open heart to the Holy Spirit."

"One of the main fruits … coming from all this process is really the experience of the synodal methodology that we call 'conversation in the Spirit.' So we hope that we can really continue the journey with this methodology. That is a way to bring together and to foster communion between people who are so diverse," Sister Nathalie told OSV News.

Sister Nathalie is used to navigating turbulent waters: She is a sailor, and that's how she formed young people when she ran youth ministry programs in her native France.

"That's the church today. The church is very diverse, and there are different visions. There are tensions. That's part of the journey," she said. "But at the end -- and Pope Francis likes to repeat that every time he speaks about synodality -- at the end, the Holy Spirit brings harmony. So that's what we hope -- that the synod will continue to foster communion to allow the participation of all, so that we are a more missionary church to better serve the people of today."

For her, the most important word of this synod is "together." In a world so polarized with violence and division, she said, "it's really about that, about togetherness."

"If you look at the members, you have a diversity of members. That was already the experience in the continental phase. Especially in Europe, you have very, very different visions between Western Europe and the church in Eastern Europe. But they said (in the first phases of the synod) it was the first time they could really listen to each other, understand more (of) why the others have another view," she said.

Recalling her own experience, she said, "Each local church is also very much shaped by the context, the culture, the societies, the history of the society and of the church. So we need to understand that we have one face, but expressed in different ways, because we are not coming from the same context and the same culture, and we have different lenses."

"But really, I think what we hope is that we understand more and more, as Pope Francis said, that unity is not about uniformity, but about the diversity in which there is a dialogue among all. And a mutual listening and trying to have a mutual understanding," Sister Nathalie said.

According to the Vatican, the Sept. 30 prayer vigil prior to the synod opening will be a "celebration of gratitude centered on four gifts": gratitude for the gift of unity and for the synodal journey, for the gift of the other, for the gift of peace and for the gift of creation.

The vigil will include listening to the Word of God, praise and intercession, Taizé songs and silence -- "a strong sign of fraternity, unity and peace," the Vatican said.

"The ecumenical dimension of the synod is very, very important," Sister Nathalie told OSV News. "And through all this dialogue -- to foster unity among the different Christian churches and communities (is important). We need to learn this exchange of gifts. That doesn't mean that we all have to be exactly the same way.

"But we share one baptism, one faith, and we follow Christ," she continued. "I see that this synod is also helping us to learn more and more how to be one church united, but with and through diversity, because at the end that's the code of God: 'May all be one so that the word believes,'" a reference to John 17:20-23.

Thousands of young adults ages 18 to 35 from various countries also will take part in a program of workshops and meetings around Rome Sept. 29-Oct. 1, as part of a synodal "Together" program, the Vatican announced.

Workshop themes include hearing refugees share their experiences, learning from other denominations and faiths, visiting the work of the city missions to the marginalized, recognizing Christ in the diversity of Catholic traditions, ecumenical panel discussions and caring for creation.

Sister Nathalie, who spoke to OSV News during World Youth Day in Lisbon, Portugal, said that young people are crucial for the synodal process.

"A synodal church is a church for everybody, with everybody listening to everybody. So it's very important to connect with young people, especially (because) during the consultation (phase) and the continental meetings, the topic of young people was one of the main concerns. How can we connect better with young people, reach them, proclaim the gospel to them," she said.

"I always say, if we are living this synod now, it's a fruit of the synod on youth, because through the synod on youth, we have understood that young people want to be listened to," she said of the 15th world Synod of Bishops that took place in Rome in 2018 that is commonly referred to as the Synod on Young People.

For Sister Nathalie, WYD in Lisbon was a perfect preparation for the synod in Rome. It was a "gift" to be there, she said, "also to experience synodality."

"Young people, priests, bishops, men and women, consecrated people" were "journeying together," she said, which she saw as "synodality in action."