ISTANDBUL — During the only public Mass of his three-day apostolic journey to Turkey, Pope Francis warned that unity without the Holy Spirit stays limited within human plans and falls into mere uniformity.

Celebrating the Mass in the Salesian-run Catholic Cathedral of the Holy Spirit in Istanbul, Pope Francis began his reflection Saturday by turning to the day’s Gospel reading from John, in which Jesus speaks of himself as “the font from which those who thirst for salvation draw.”

In this passage, Jesus refers to “the gift of the Holy Spirit” given to the disciples after Christ’s death and resurrection.

“The Church’s whole life and mission depend on the Holy Spirit,” the Pope said.

Saturday’s Mass was celebrated hours after Pope Francis arrived in Istanbul, Turkey’s largest city, on day two of his Nov. 28-30 journey to the nation. It was attended by the patriarch of Constantinople, Bartholomew I, with whom the Holy Father will meet later in the day.

Earlier in the day, the Pope made a visit to the city’s iconic “Blue Mosque,” followed by the Hagia Sophia Museum.

Citing the day’s first reading taken from St. Paul to the Corinthians, the Holy Father said the “the profession of faith itself ... is only possible because it is prompted by the Holy Spirit.”

The movement to pray, to encounter others, to forgive and to love, he said, “is the Spirit, who has taken hold of us.”

Although the charisms which the Holy Spirit “brings forth” in the Church may at first appear to “create disorder,” he said, they in fact “constitute an immense richness, because the Holy Spirit is the spirit of unity."

Pope Francis made the distinction between “unity,” which can only be brought about through the Holy Spirit, and “uniformity.”

“When we try to create unity through our own human designs, we end up with uniformity and  homogenization.”

The Holy Father continued, “If we let ourselves be led by the Spirit, however, richness, variety and diversity will never create conflict, because the Spirit spurs us to experience variety in the communion of the Church.”

Pope Francis spoke of the constant temptation “to resist the Holy Spirit,” who “takes us out of our comfort zone and unsettles us” and “makes us get up and drives the Church forward.”

“In truth, the Church shows her fidelity to the Holy Spirit in as much as she does not try to control or tame him.”

As Christians, he said, we “become true missionary disciples, able to challenge consciences, when we throw off our defensiveness and allow ourselves to be led by the Spirit.”  

These “defensive mechanisms,” whereby we become “entrenched within our ideas and our own strengths,” impede understanding and “sincere dialogue” with others.

“But the Church, flowing from Pentecost, is given the fire of the Holy Spirit, which does not so much fill the mind with ideas, but enflames the heart,” Pope Francis said.

Rather, “she is moved by the breath of the Spirit, which does not transmit a power, but, rather, an ability to serve in love, a language which everyone is able to understand.”

Pope Francis concluded his homily by invoking the Virgin Mary, who awaited Pentecost in the Upper Room alongside the apostles.

“Let us pray to the Lord, asking him to send his Holy Spirit into our hearts and to make us witnesses of his Gospel in all the world.”