Alessandra Tarantino / AP

A pope and and a secular Jew from Vermont walk into the lobby of a Vatican guesthouse. They shake hands. It was nothing, the pope maintains. “If someone thinks that greeting someone means getting involved in politics,” he said, “I recommend that he find a psychiatrist!”

There’s a punchline in there somewhere, but this is not a scene drawn from the rabbi-priest-joke canon. On Saturday, Bernie Sanders met Pope Francis in Rome, greeting the pontiff as he departed for Greece. The senator had been invited to speak on “the moral economy” at a conference at the Pontifical Academy of Social Science, and the speculation was fierce: Will he meet the pope, or won’t he? Although Federico Lombardi, a Vatican spokesman, suggested before the trip that a meeting wouldn’t happen, Sanders got his wish. According to The New York Times, a personal secretary to the pope found Sanders while he was at dinner and told him where and when to be if he wanted to catch Francis. It may be mostly one-sided, but the love affair of Bernie and Francis is not unrequited: Against all logic, the world’s foremost Catholic theologian and a socialist who’s running for United States president have found a jam.

On its face, the affinity between the two men might seem obvious. Both speak critically about capitalism, wealth, and greed; both seem to connect economic issues to the rest of the world’s ills. Sanders has pulled Francis close throughout his campaign, praising the pontiff ardently after he spoke to Congress last September, for example. Perhaps Sanders is hoping to soak up some of the pope’s massive popularity, or feels naturally drawn toward the other 70-something white man who has recently become an unlikely icon of progressive values. His affection seems heartfelt, though. As he told the press when news of his trip became public, “I was very moved by the invitation.”

Let these seeming similarities lead us not into temptation: The alliance between Sanders and Pope Francis is profoundly odd. For one thing, Catholic teachings don’t necessarily line up with Sanders’s stump speech as much as he might like to think. The conference he attended at the Vatican was gathered to commemorate Centesimus annus, Pope John Paul II’s 1991 encyclical that focused on the evils of Marxism and communism. In that document, John Paul II argued that economies exist to serve human freedom, the core of which is “ethical and religious.” He criticized a kind of thinking that “totally reduces man to the sphere of economics and the satisfaction of material needs.” While Sanders has called for economic policies that focus more on poverty than profit-seeking and that incorporate goals like care for the environment, he is absolutely a material thinker. He apparently believes that every policy area, from foreign affairs to women’s rights, can be explained by economic factors; politics, in his view, is neither ethical nor religious, but rather a function of wealth and class. His campaign-trail preaching seems to be in conflict with the very document he flew to Rome to celebrate—not to mention central Church teachings on topics like contraception and abortion, which directly contradict Sanders’s platform.

This gets at the deeper weirdness in the Bernie-Francis axis: Sanders has washed the pope in secularism. Last week, he annotated a speech Francis made in Bolivia for The Washington Post, highlighting the pope’s call for radical changes on environmental and economic policies. The parts of the speech he assiduously avoids, though, are the ones that mention Jesus. The global system of capitalism “runs counter to the plan of Jesus, against the Good News that Jesus brought,” Francis said. “Working for a just distribution of the fruits of the earth and human labor is not mere philanthropy. It is a moral obligation.” Sanders’s marginalia explains this as a “calling for a social and economic system that lives in harmony with nature.”

It goes on. Francis calls the “unfettered pursuit of money” the “dung of the devil,” describing it as “evil”—something he believes is literal, along with a literal Satan. Sanders says this is Francis “asking us to become a different kind of person, where our happiness and well-being comes from serving others and being part of the human community.” In the prepared version of his speech at the Vatican conference, Sanders remarked that “our very soul as a nation has suffered as the public lost faith in political and social institutions”—with both “soul” and “faith” meant metaphorically rather than metaphysically, of course.

To a certain extent, Francis participates in his own secularization. Out in public, he speaks in broad, universal terms, intentionally looking for ecumenical space in the Church for non-Catholics and nonreligious people alike. Read any of his formal writings and it becomes clear that his is a particularist vision: He believes work for and with the poor is the Church’s mission, “focused on Jesus Christ,” and is a way to “proclaim the message of salvation.” But he’s skilled at secular translation, calling on atheists and believers alike to “do good,” a vague formulation of ethical uprightness that any humanist could probably get behind. This is part of why some American conservatives tend to critique the current pope: They think he has softened the hard theological boundaries that make Catholic theology distinctive.

When Sanders speaks about Francis, he’s doing his own kind of translation magic act. In his annotation of the pope’s Bolivian speech, Sanders alludes to a global “human community” and speaks of cheerful things like “happiness” and “serving others”—rather than, say, his support for Nicaragua’s Sandinistas, a position strongly countered by the institutional Church in the 1970s and ’80s. In Rome, Sanders said, “There are few places in modern thought that rival the depth and insight of the Church’s moral teachings on the market economy.” With that phrasing, it’s easy to imagine Rerum Novarum, the Church’s foundational encyclical on economic and social issues, sitting on Bernie’s shelf right next to his copy of the The Marx-Engels Reader—although the encyclical, in many ways, was intended to provide an alternative to socialism, not an endorsement of it.

For now, Sanders has gotten his handshake, and the so-called “cool pope” may win a little more cred from progressive American Millennials who have a selective understanding of Catholic teachings and history. The encounter between the pope and the Vermont senator is a revealing glimpse of the careful public personas the two men have cultivated, which is perhaps their truest point of overlap: They are representatives of specific theological principles and political ideologies that have been carefully rendered into anodyne humanism. In a secular age, that may be the secret to their popular appeal.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.