VATICAN CITY, MARCH 24, 2002 ( Man´s real strength lies in fidelity to truth, John Paul II told the faithful gathered in St. Peter´s Square for Palm Sunday Mass.

The Pope followed the Mass from the atrium of St. Peter´s Basilica, having been persuaded by his doctors not to preside over the lengthy liturgy. An arthritic right knee has plagued him since the end of February.

The Holy Father was almost constantly on his knees during the Mass. He also blessed the palms and delivered the homily at the Mass commemorating Jesus´ triumphal entrance into Jerusalem. But he let his vicar for Rome, Cardinal Camillo Ruini, celebrate the liturgy.

Today the Diocese of Rome was celebrating a Youth Day, and the presence of young people in St. Peter´s Square was evident, especially during the Palm Sunday procession. Young people came from Canada, France, Germany, Croatia and Spain, among other countries.

Young people also read the Prayers of the Faithful, in Polish, Arabic, French, Tagalog, Portuguese and German.

"The one you have chosen as Master is not a merchant of illusions, not one of the powerful of this world, nor an astute and clever thinker," the Pope said during his homily. "You know whom you have decided to follow: He is the Risen Crucified One! Christ who died for you, Christ who rose for you."

"And I assure you that you will not be disappointed," the Pontiff added.

"Man´s real strength," he continued, "is seen in the fidelity with which he is capable to render witness to truth, resisting blandishments and threats, incomprehension and blackmail, including harsh and merciless persecution."

"Only if you are willing to do this, will you become what Jesus expects of you, namely ´salt of the earth´ and ´light of the world,´" the motto of the World Youth Day scheduled for July 23-28 in Toronto.

"Dear young people, do not lose your flavor of Christians, the flavor of the Gospel!" the Pope concluded, raising his voice. "Keep it alive by constantly meditating on the paschal mystery: May the cross be your school of wisdom!"

At the end of the Mass, the Holy Father introduced the Angelus and, speaking in Italian, French, English, German, Spanish, Portuguese and Polish, invited young people worldwide to the World Youth Day in Canada.