Pope Francis warned Saturday that the “easy answers” of populism and authoritarianism are threatening democracy in Europe and called for fresh dedication to promoting the common good.

Arriving in Greece, the birthplace of democracy, Francis used a speech to Greek political and cultural leaders to warn Europe at large about the threats facing the continent. He said only robust multilateralism can address the pressing issues of the day, from protecting the environment to fighting the pandemic and poverty.

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“Politics needs this, in order to put common needs ahead of private interests,” Francis said. “Yet we cannot avoid noting with concern how today, and not only in Europe, we are witnessing a retreat from democracy.”

Later Saturday, Francis met with the leader of Greece’s Orthodox Church, Archbishop Ieronymos, and was briefly heckled as he arrived at the archbishop’s residence.

“Pope, you’re a heretic!” an elderly Orthodox priest shouted three times before police took him away. Francis appeared not to notice and proceeded inside, but the disturbance was a reminder of the lingering tensions between Catholics and Orthodox Christians in Greece.

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Francis, who lived through Argentina’s populist Peronist era as well as its military dictatorship, has frequently warned about the threat of authoritarianism and populism and the danger it poses to the European Union and democracy itself.

He didn’t name any specific countries or leaders during his speech. The EU, however, is locked in a feud with members Poland and Hungary over rule-of-law issues, with Warsaw insisting that Polish law takes precedence over EU policies and regulations.

Outside the bloc, populist leaders in Brazil and the administration of former U.S. President Donald Trump pressed nationalist policies on the environment that contrasted sharply with Francis’ call to care for “our common home.”

Opening the second leg of his five-day trip to Cyprus and Greece, Francis recalled that it was in Greece, according to Aristotle, that man became conscious of being a political animal and a member of a community of fellow citizens.

“Here, democracy was born,” Francis told Greek President Katerina Sakellaropoulou. “That cradle, thousands of years later, was to become a house, a great house of democratic peoples. I am speaking of the European Union and the dream of peace and fraternity that it represents for so many peoples.”

That dream is at risk amid the economic upheaval and other disruptions of the pandemic that can breed nationalist sentiments and make authoritarianism seem “compelling and populism’s easy answers appear attractive,” Francis said.

“The remedy is not to be found in an obsessive quest for popularity, in a thirst for visibility, in a flurry of unrealistic promises … but in good politics,” he said.

As an example, Francis praised the “necessary vaccination campaign” promoted by government authorities to tame the coronavirus. He referenced another Greek doctor-philosopher – Hippocrates – in response to vaccine skeptics and virus deniers, who count many religious conservatives among them.

Francis cited the Hippocratic oath to not only do what is best for the sick, but to “abstain from whatever is harmful and offensive to others,” especially the elderly.

Greece’s president the sentiment in her speech. “The virus spreads and mutates, helped by the irrational denial of reality and inequalities in our societies,” Sakellaropoulou said.

Greece is grappling with its highest level of coronavirus infections since the start of the pandemic with deaths approaching record levels. A quarter of the country’s adults remain unvaccinated, and Parliament recently approved a vaccine mandate for people over age 60.

Francis’ trip has been clouded by the Dec. 2 death of the Vatican’s ambassador to the European Union, Archbishop Aldo Giordano. He and the president of the Italian bishops’ conference were among several prelates who tested positive after celebrating Francis’ final Mass in Slovakia in September.

The Vatican’s EU embassy insisted that Giordano caught the virus days earlier during a European bishops’ meeting in Hungary.

Francis’ visit to Cyprus and Greece also has focused on the plight of migrants as Europe hardens its border control policies. He is scheduled to travel Sunday to the Aegean Sea island of Lesbos, where he visited five years ago to meet with migrants at a detention camp.

In Athens, Francis is also met with Archbishop Ieronymos, the head of Greece’s Orthodox Church.

In 2001, Pope John Paul II became the first Catholic leader to visit Greece in more than 1,200 years and he used the occasion to beg forgiveness for the sins “by action or omission” of Catholics against Orthodox over the centuries. Francis’ visit 20 years later is expected to further try to heal Catholic-Orthodox ties, still wounded by the Great Schism that divided Christianity as evidenced by the heckling incident Saturday.

Francis has accelerated inter-faith initiatives, as the two churches attempt to shift from centuries of competition and mistrust toward collaboration.

Orthodox churches are also seeking alliances amid a deepening dispute over the independence of the Ukrainian church, which was historically governed by the Russian Orthodox Church.

“I think the presence of the pope in Greece and Cyprus signals a return to the normal relationship that we should have … so that we can move toward what is most important of all: the unity of the Christian world,” Ioannis Panagiotopoulos, an associate professor of divinity and church history at Athens University, told The Associated Press.

Up to 4,000 police officers were readied for duty in Athens for the pope’s visit, and authorities banned protests and large public gatherings in parts of central Athens over the weekend.

The pope’s visit ends Monday.