Early on, the Beatles made a show of conformity. With their mop-tops, matching outfits, and synchronized movements on stage, they were indistinguishable, if not interchangeable. But even as they began to assert their own personalities, John Lennon’s was slow to emerge. The man who wrote “Nowhere Man” had trouble finding his place. “Between reading things about ‘Paul was the musician’ and ‘George was the philosopher,’ I wonder where I fit in, you know, what was my contribution,” Lennon told Rolling Stone’s Jann Wenner in a blisteringly honest interview in 1970. “I’m a f-ing artist man, I’m not a pr agent or the product of some other person’s imagination.”

It was only in the vacuum that developed after manager Brian Epstein’s death in 1967 that Lennon began to assert himself. With the approach of the 25th anniversary of Lennon’s murder (December 8), it’s worth considering what made him the most fascinating member – personally, socially, and musically – of the world’s most important rock band.

To historians (and the Beatles are now a subject of scholarly study), the schism between John and Paul can be identified pretty early on, but it was undeniable with the1968 release of the “Hey Jude/Revolution” single. “Hey Jude,” the A-side, was a McCartney pop classic – a tuneful piano ballad proffering advice on love and courtship. The B-side, Lennon’s “Revolution,” was an entirely different animal. It opened with a searing electric guitar and a howl, the raw 1950s rock sound that Lennon always preferred. The lyrics announced a new political consciousness, one that would become more radical as time wore on.

But there was an ambivalence to Lennon’s first political statement. “If you go carrying pictures of Chairman Mao / you ain’t gonna make it with anyone anyhow,” he sings, skewering those who would use revolution as a pickup line. But he’s unsure of his own convictions. On the single he cautions, “you know we all want to change the world / but when you talk about destruction, don’t you know that you can count me out.” On the “White Album,” he wants it both ways, singing ” … you can count me out,” then adds, “in.”

By the late 1960s, the Beatles were a group in name only, and individual members were already courting the fan base with solo releases in anticipation of the impending breakup. Everyone but John, that is. If anything, he seemed determined to repel Beatles fans. More-or-less conventional singles like “Instant Karma!” and “Cold Turkey” were outnumbered by avant-garde collaborations with his new musical and life-partner, Yoko Ono. 1968’s “Two Virgins” – which famously featured nude photos of the couple on the front and back covers – was comprised of found sounds, muted conversation, and musical bric-a-brac. Side A of “Life With the Lions,” their follow-up, had John playing electric guitar while Yoko wailed like a colicky baby for 26 minutes. “The Wedding Album” was 45 minutes of messy verbal collage. They tested the faith of even the most devoted fans.

John’s public life was equally shocking to many. After their March 1969 wedding, John and Yoko – now mockingly referred to as “Joko” by the press – held a “Bed-In for Peace” in the presidential suite at the Amsterdam Hilton. It was during a similar event in Montreal that Lennon wrote “Give Peace a Chance,” the Hari Krishna-inspired chant that he envisioned as an update and successor to “We Shall Overcome” for the international peace movement.

John was relishing, and flaunting, his newfound freedom. “I’m not a mop top any more,” he told his eventual biographer Ray Coleman in 1969. “I can say what I like!” He had come to consider himself not just a musician or activist, but an artist – like Andy Warhol, Salvador Dali, and Marcel Duchamp – for whom publicity was integral to his art.

Lennon’s antics and relationship with Ono (who many fans blamed for the breakup of the Beatles) earned him plenty of scorn, a subject he addressed in the “The Ballad of John and Yoko”: “The newspapers said, ‘she’s gone to his head, they look just like two gurus in drag’ / Christ, you know it ain’t easy, you know how hard it can be / the way things are going, they’re gonna crucify me.” But a poll conducted in 1969 among the readers of the British magazine Disco and Music Echo found that John had, for the first time, surpassed Paul as Britain’s favorite Beatle.

His reputation would only grow with his 1970 album “Plastic Ono Band,” the high-water mark of his post-Beatle career, recorded just after he and Yoko underwent primal scream therapy with Dr. Arthur Janov. Lennon is singing from a freshly opened wound, particularly on the topic of his own childhood abandonment by his parents. “Mother,” the album’s opening track, ends with him singing – then primal-screaming – “Mama don’t go / Daddy come home.” He would be more anthemic on “Imagine” (1971), more stridently political on “Sometime in New York City” (1972), but nowhere was he as raw, direct, and consistently brilliant as here.

“Working Class Hero” is an equally unflinching look at class and power structures, the most vitriolic protest song since Dylan’s “Masters of War.” But the album’s centerpiece is the mournful “God.” It begins with the gnomic line, “God is a concept by which we measure our pain,” then proceeds to catalog Lennon’s fallen idols (or those of his generation, anyway) – “I Ching,” Jesus, Kennedy, Buddha, Elvis, Zimmerman, the Beatles. It closes with his famous eulogy for the 1960s: “The dream is over, what can I say / the dream is over, yesterday / I was the dreamweaver, but now I’m reborn / I was the walrus, but now I’m John / And so dear friends, you’ll just have to carry on.”

The song took on new poignancy with Lennon’s murder in 1980, at a time when he was no longer at the center of the political maelstroms he had so blithely danced into in his earlier life. Nor was he the figure of mass adulation he had once been. In fact, he had just emerged from a five-year seclusion, during which he’d dedicated himself to raising his son Sean, to release “Double Fantasy,” a modest collection of songs about quiet pleasures and new beginnings.

Lennon was shot in front of his apartment building on the evening of December 8, 1980, by Mark David Chapman, a 25-year-old hospital security guard who claims to have been a lifelong Lennon fan. He was apparently motivated neither by politics nor by any personal grievance. He had succeeded in getting Lennon’s autograph earlier that very day. It is the bitterest irony that an outspoken pacifist should die so violently, and that a man who stood for so many things should die for no reason at all.