Throughout its modern history, however, the “European project,” as the Continent’s current faltering push for unity is known, has sought to keep religion and the unruly passions it can stir at arm’s length. The 1951 Treaty of Rome and other founding texts of what is today the European Union make no mention of God or Christianity. The Brussels bureaucracy, in its official account of Mr. Heitz’s religion-tinged flag, ignores the Virgin Mary, stating instead that the 12 stars “symbolize the ideal of unity, solidarity and harmony among the people of Europe.”

“There is a general suspicion of anything religious, a view that faith should be kept out of the public sphere,” said Gudrun Kugler, director of the Observatory on Intolerance and Discrimination against Christians, a Vienna-based research and lobbying group. “There is a very strong current of radical secularism,” she said, adding that this affects all religions but is particularly strong against Christianity because of a view that “Christianity dominated unfairly for centuries” and needs to be put in its place…

For the European Union’s most strident critics, the dispute has been a godsend, buttressing their argument that Brussels is an alien, meddling and sinister force. “I need to voice a serious and disturbing suspicion: that the E.U. is under the control of Satan or Satanism,” said Rafael Rafaj of the Slovak National Party, a far-right nationalist party.