It started with a dumb ox.

Robert Barron was a student at Fenwick High School in Oak Park, Illinois. A young Dominican friar taught the class one of St. Thomas Aquinas’ arguments for God’s existence when Barron was 14.

“And for some reason it had this huge impact on me,” Father Barron said of Aquinas, “the dumb ox.” “It goes back to my teenage years and Thomas Aquinas and a sense of the reality of God that I’ve never really lost. I’d put it that way — that God exists and that God is the supreme good and that our lives should be focused on him.”

Father Barron, president/rector of the Archdiocese of Chicago’s Mundelein Seminary and founder of Word on Fire, a global media ministry, has been named auxiliary bishop of the Archdiocese of Los Angeles. Father Barron, along with Msgr. Joseph V. Brennan and Msgr. David G. O’Connell, will be ordained auxiliary bishops this fall.

Father Barron received the call about his appointment from the papal nuncio, Archbishop Carlo Maria Viganò, while he was watching golf.

“It was a complete surprise,” he said. “I’m excited about it. There’s a fear, and it’s something new. But I’m excited. I mean, Los Angeles. There’s a lot going on and it’s a pretty vibrant Church.”

Shortly after his ordination on May 24, 1986, Father Barron served as associate pastor at St. Paul of the Cross Parish in Park Ridge, Illinois.

He was appointed to the theological faculty of Mundelein Seminary, and has served as a visiting professor at the University of Notre Dame and at the Pontifical University of St. Thomas Aquinas in Rome, as well as scholar in residence at the North American Pontifical College at the Vatican.

“‘I very much identify with Pope Francis’ call for the New Evangelization, which is very much a continuation of the call that began with St. John Paul II and continued through Benedict,” Father Barron said.

“For a long time, what I’ve tried to do in my own work is lead with the positive, lead with the joyful, lead with the articulation of the life,” he said of his teaching and his Word on Fire ministry.

“I think for too long we’ve been identified as finger waggers. Here’s what you don’t do. Don’t do this, don’t do this,” he explained. “For me, that’s not the right evangelical strategy. You get to those ‘don’ts.’ But you begin with the life.”

He compared the strategy to teaching a child about baseball. You don’t begin with the arcane rules, but by bringing a child to a game to appreciate its beauty — these are great plays, these are great players.

So too with the faith.

“You start with the saints, you start with the glory of the life of Christ, you start with how lives are transformed with contact with him,” he explained. “That’s why I love those tapestries [in the Cathedral of Our Lady of the Angels]. You look at the saints.”

While Father Barron expects to continue his work with Word on Fire, he has no question about his priority ministry.

“I have to present to this archdiocese and its people,” he said.

Father Barron has been a regular speaker at the annual Religious Education Congress, serving as keynote in 2014. He has also spoken at St. John’s Seminary, among other locations in the archdiocese.

He will be giving the opening address at the World Meeting of Families in Philadelphia in September and will provide commentary for the papal visit to the United States on NBC.

“The Mystery of God: Who God Is And Why He Matters,” a film and study program by Father Barron and Word on Fire, is due out this fall.

Father Barron and NBC Today show correspondent Mike Leonard worked together to produce “Catholicism,” an award-winning series about the Catholic faith.