Yes, even US President Donald Trump is welcome in the Vatican. Between his visit to the Wailing Wall in Jerusalem and the NATO summit in Brussels, the US president is making a stopover in the Vatican to meet Pope Francis.

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In 2013, Donald Trump tried, in his own way, to reach out to the pope. "The new Pope is a humble man, very much like me, which probably explains why I like him so much!" he tweeted on December 25, 2013.

His attempt to reach out failed miserably. The two men have diametrically opposed attitudes on humility. In picking the name Francis, the current pope chose to honor the founder of the Franciscan Order, St. Francis of Assisi, a man who abandoned a life of luxury for Christian austerity. Donald Trump, on the other hand, is known for his opulent and freewheeling lifestyle.

Building walls is 'not Christian'

The two leaders have unbridgeable ideological differences when it comes to the current refugee crisis. After his visit to the Greek island of Lesbos in 2016, Pope Francis granted 12 Muslim refugees asylum in the Vatican. Trump, on the other hand, issued an executive order shortly after his inauguration banning banning people from seven predominately Muslim countries from entering the US.

Their most pointed exchange happened in February 2016. "A person who only thinks about building walls, wherever they may be, and not building bridges, is not Christian," Pope Francis said on his flight back from Mexico when asked about Trump's vow to build a wall along the Mexican border.

Trump refused to let that comment from the head of the Catholic Church pass. "If and when the Vatican is attacked by ISIS, which as everyone knows is ISIS's ultimate trophy, I can promise you that the Pope would have only wished and prayed that Donald Trump would have been President because this would not have happened," Trump responded, adding that he could not care less what the pope said.

Some common ground

Despite the great gulf separating the Protestant businessman from New York and the Latin American priest from Buenos Aires, closer examinaton reveals some common ground between the two men.

Both rose as outsiders, defying the hierarchy of their respective institutions, and both are struggling with criticism from within their own ranks. And Pope Francis, like President Trump, is not averse to spontaneous staff shake-ups.

In January 2015, the pontiff dismissed the commander of the Swiss Guard, Daniel Rudolf Anrig, because he was allegedly "too strict." And the gay Polish priest Krysztof Charamsa, assistant secretary of the International Theological Commission of the Congregation for the Doctrine of the Faith, was suspended after publicly announcing that he was gay in October 2015.

Open doors in the Vatican

In view of all the differences and the little they have in common, the meeting of the two elderly gentlemen behind closed doors will likely be nothing more than an exchange of opinions.

"There are always doors that are not closed. We need to find the doors that are at least partly open, go in, and talk about things we have in common and go forward, step by step," said Pope Francis, according to Radio Vatican. "Topics will emerge in our conversations. I will say what I think and he will say what he thinks. But I have never wanted to make a judgement without first listening to the person."

Clearly, the pope is not overly thrilled about the visit. He did not actually invite the US president; it was Trump who asked for the audience. Perhaps his only aim is to get a good shot of himself with the pope for the media. For its part, the Vatican is fulfilling a diplomatic duty, as there are no real opportunities for strategic cooperation to be gained from the visit. 

It is hard to say what Trump's mission is. He's hardly a prodigal son intent on  leaving behind his current lifestyle to return to the fold. And as the father of five children from three different marriages, he's certainly no role model for Catholic morality or family life.

PR stunt for Trump?

After his arms deal with Saudi Arabia, Trump will also not be scoring any points as a peacemaker. The only thing that remains is an ambiguous hope for an undefined religious and political dialogue to be initiated in the Middle East by Trump's Jewish son-in-law and advisor, Jared Kushner.

"Trump's advisors hope to spread a message of 'unity, peace, tolerance and hope' with regard to interaction between the three great religious communities, Islam, Judaism and the Catholic Church - of course, under the direction of the US president," Rome correspondent Julius Müller-Meiningen wrote in Christ & Welt (Christ and the World), a supplement of the weekly German newspaper, Die Zeit. "It sounds so pompous and it also contradicts the anti-Islamic stance of the Trump administration, so one cannot let go of the suspicion that this is a PR measure."