ABOARD THE PAPAL FLIGHT FROM ROMANIA (CNS) -- Pope Francis said that he continues to visit retired Pope Benedict XVI, 92, who is like a grandfather who continues to encourage him and give him strength.

"I take his hand and let him speak. He speaks little, at his own pace, but with the same profoundness as always. Benedict's problem are his knees, not his mind. He has a great lucidity," the pope told journalists June 2 on his return flight from Romania. The pope spent about 35 minutes with reporters on the short flight, answering five questions.

When asked about his relationship with this predecessor, the pope said his conversations with Pope Benedict make him stronger and he compared the knowledge he receives from his predecessor as the sap "from the roots that help me to go forward.

"When I hear him speak, I become strong," he explained. "I feel this tradition of the church. The tradition of the church is not a museum. No, tradition is like the roots that give you the sap in order to grow. You won't become the root; you will grow and bear fruit and the seed will be root for others."

Recalling a quote by Austrian composer Gustav Mahler, the pope said that tradition "is the guarantee of the future and not the custodian of ashes."

"The tradition of the church is always in motion," he said. "The nostalgia of the 'integralists' is to return to the ashes," but that is not Catholic tradition; tradition is "the roots that guarantee the tree grows, blossoms and bears fruit."

Referring to his remarks in Romania about unity and fraternity, the pope was asked about growing divisions within the European Union.

Unity on the continent is a task for every European country, he said. "If Europe does not guard well against future challenges, Europe will wither away," he warned. While cultural differences must be respected, Europeans must not give in "to pessimism or ideologies."

Pope Francis also was asked about an event in the Romanian Orthodox Cathedral in Bucharest June 1 and how it appeared that many people at the gathering did not join in reciting the Lord's Prayer.

Where there is tension or conflict, the pope said, Christians must have "a relationship with an outstretched hand."

"We must go forward together," he said, "always keeping in mind that ecumenism isn't about arriving at the end of the game. Ecumenism means walking together, praying together, an ecumenism of prayer."

Christians also share "an ecumenism of blood, an ecumenism of witness and what I call 'an ecumenism of the poor' -- working together to help the sick, those who are on the margins."

Pope Francis said that that Chapter 25 of St. Matthew's Gospel -- where Jesus says those who feed the hungry, clothe the naked, visit the sick and prisoners do the same for him -- "is a good ecumenical program."

"It is possible! It is possible to walk together in unity, fraternity, hand outstretched, thinking well of each other, not speaking ill of others," he said. Every church has those opposed to Christian unity, who call others "schismatics."

"We all have defects but if we walk together, we leave the defects aside," the pope said. "Let the old bachelors criticize."