ANNAPOLIS, Md. — ONE year into his astonishingly popular papacy, Pope Francis has become the perfect divining rod for uncovering assumptions about the future of the Catholic Church.

After an interview last week, during which he responded to a question about civil unions with a discussion of how “secular states” used them “to regulate different situations of cohabitation,” some mainstream media outlets reported that he had signaled a new openness to same-sex unions. More cautious analysts countered that he had done nothing of the kind.

Wishful thinking is rampant where Francis is concerned, perhaps especially among those born into the faith who have grown distant from it. While a recent Pew poll suggests that church attendance in America has not risen with the pope’s steady stream of positive press, the image he projects of a kinder, gentler Catholicism has inspired many of the lapsed, the recovering, the former and the fallen to reconsider the possibilities of being Catholic without qualification.

Yet even as the pope appears to be opening a big tent, others in the church hierarchy ensure that it will not expand too far. Last July, in response to a question about gay priests, Francis famously uttered one of the lines that set the tolerant tone of his pastoral style, “Who am I to judge?” That same month, the Archdiocese of Detroit published a warning against “nearly a dozen churches” in its jurisdiction that “use the name Catholic, but aren’t.”...