Pope Francis told a group of young people Sunday that the devil is not a fairy tale but truly exists, and that he is their “biggest enemy.”

In a meeting with children and young people from Saint Crispin’s parish in Viterbo, the pope said that the devil is “the ruler of the pagan spirit” and “the lord of evil,” while urging them to resist his wiles through prayer and recourse to Jesus.

In a spirited dialogue with the group, Francis asked question after question regarding the devil and how he attempts to separate us from God.

“The devil! But the devil is a fantasy, he does not exist, right?” the pope asked teasingly. “Isn’t he just an old wives’ tale?”

“Yes, he exists, it’s true, and he is our biggest enemy,” he agreed with them. “He is the one who tries to make us slip up in life. He is the one who puts bad desires and bad thoughts in our hearts and leads us to do bad things, many bad things in life, ending with war.”

Pope Francis has often spoken of the devil during his 6-year pontificate, insisting that he is not a myth and must be combatted.

During his U.S. visit in 2015, the pope told Harlem schoolchildren that the devil works to destroy our dreams and undermine our happiness.

Satan “sows sadness, sows distrust, sows envy, and sows evil desires,” he said. “The devil always sows sadness because he doesn’t want us happy. He doesn’t want us to dream.”

“Where there is joy, Jesus is always present,” Francis said. “Because Jesus is joy, and he wants to help us so that his joy stays with us every day.”

On Sunday, the pope offered the Italian children of Viterbo a similar message, insisting that the devil can never be our friend, since he only wishes to harm us. “He will take us on the path of evil, to do evil things,” he said.

Jesus is the one who defends us from the devil, he said, since “He is the Lord, He commands.” It was Jesus who cast out devils on earth, chasing the evil one away.

In his ongoing reflection, the pope said the devil has “many qualities,” one of which is his intelligence.

“He is very intelligent, more intelligent than theologians!” he said. “He is very intelligent and this is a quality.”

But the devil’s “greatest quality,” he continued, is his ability to deceive.

“The devil is a liar,” Francis said. “Because he tells you: look at how beautiful this is… And he acts in the same way a snake does with a little bird. It looks at it, it puts it to sleep and then eats it.”

“The devil shows you things and tells you: ‘This is beautiful, it will do you good, do not obey your father and mother, do not do this, go this way, it will do you good,’ and then leaves you alone and to be defeated,” he said.

“In the gospel, he is called the father of lies,” the pontiff continued. “God is the Father of goodness,” but the devil, who is evil, passes himself off as good by lying.

“You have to tell the devil, ‘Go away, liar!’” he told them.

The best defense against the devil is prayer, he continued.

“When the attack comes, go to Jesus, who never told a lie,” he said. “Jesus cannot tell lies. Jesus always tells us the truth. Sometimes we do not like it, because there are some painful truths, but He tells them.”

Francis also told the children that the devil promises happiness, yet never delivers.

What the devil offers is like candy, he continued. You eat one, then another, then a dozen, and then at night you wind up with a stomach ache.

“Yes, a stomach ache,” the pope said. “The devil gives you momentary joy and then you get a ‘stomach ache’ of the soul. Your soul is sick. The Holy Spirit, on the other hand, gives you the joy that does not make you sick.”

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