In a fleeting Instagram story in early August, the pop star Britney Spears announced that she had just returned from mass and was “a Catholic now.” Fans immediately recognized this faith as a departure for Spears, who was raised Baptist.

The Instagram post was deleted within a day of its appearance, but not before eliciting congratulations from fellow Catholics and incredulous commentary on Twitter with some asking whether the singer who dressed up as a Catholic schoolgirl in the provocative video for “ … Baby One More Time” (1999) was now “really” a Catholic.

This is not surprising. The religious choices of American celebrities have long invited incredulity. And it’s not just pop culture curiosity. This fascination with Spears’s religion highlights an ongoing conversation within American culture about authentic identity — something religious affiliation has long been used to determine.

Consider, for example, the doubt and derision that Sammy Davis, Jr. faced when he started telling friends and fans that he was Jewish in the late 1950s. Davis was among a small cohort of Black performers who broke through the segregated entertainment industry after World War II to find success with White audiences. Following a near-fatal car accident in 1954, Davis resurrected his career as a singer, impersonator, dancer and actor. Fitted with a glass eye to replace the one destroyed in the accident, Davis was irrepressibly energetic. The source of his renewed confidence, he soon explained, was Judaism.

Fellow comedians — many of them Jewish — roasted Davis for combining Blackness and Jewishness. At Davis’s bachelor party in 1960, Milton Berle, in drag, performed a parody, “My Yiddish Mau Mau,” while Peter Lawford sang, to the tune of “The Lady is a Tramp,” “That’s Why That Sammy is a Jew.” Eager to show he was in on the joke, Davis wore out punchlines about the seeming incongruity of his identities. His golf handicap, he deadpanned, was being “a one-eyed Negro who’s Jewish.”

African American Christians leveled harsher criticism in the pages of Black-owned magazines such as Ebony, questioning whether Davis had abandoned Blackness when he chose Judaism. One fellow entertainer suggested the conversion was a “gratuitous” effort to curry favor with Jewish nightclub owners and audiences. Although non-White Jews exist throughout the world, a biographer concluded that Davis became Jewish as part of an effort to become White. This narrow understanding of Jewish identity, laced with casual anti-Semitism, greeted Davis’s conversion then and since.

All of these naysayers implicitly questioned whether Davis possessed the moral seriousness — or the intellectual consistency — necessary to make such a life-altering decision.

But Davis could not have been more earnest about his Jewishness — and in fact, he considered it a natural extension of his civil rights activism. Nothing could be more logical, he argued, than to find common themes between the historic struggles of Jews against anti-Semitism and the contemporary challenges facing African Americans in a segregated nation. The idea of an inherent harmony between Black and (White) Jewish concerns papered over considerable disparities of power and priorities in 20th-century social movements, but Davis was resolute in finding political as well as historical parallels.