Then there are the books — the new biographies and deconstructions and collected interviews. He permeates our cultural oxygen like a latter-day Shakespeare. As with Shakespeare, his words are often applied in ways that their creator most likely never intended. To borrow from W.H. Auden’s “In Memory of W.B. Yeats”: “The words of a dead man/Are modified in the guts of the living.”

Mr. Sondheim, who specialized in portraits of yearning outsiders, would probably regard his canonization on Broadway with the deeply mixed feelings in which he specialized. (Surely, he would have cocked an eyebrow at his apotheosis as the warm and comforting spirit guide that seemed to materialize at that recent performance of “Into the Woods.”) While he seemed to reinvent himself with each new show, his works have always centered on a sense of human isolation, and those who perceived the composer in his early years as too clever by half failed to notice the attendant pain that underlay so much of what he wrote.

It is the empathic awareness of that pain, I think, that has kept us hooked on his work — not any omniscient wisdom but his ability to summon so clearly our confused, contradictory humanity. Ravishing individual songs may reassure us that no one is alone but, in the five decades since “Company” made his reputation, Mr. Sondheim had been creating group portraits of a crowded world where loneliness was an existential fact. When he writes, “No one is alone,” it hurts so much precisely because we sense that it is ultimately a falsehood.

It should be noted that, when he was alive, Mr. Sondheim was aware of and amused by rampant tendencies to deify him. Consider this sardonic ditty from a show called “Sondheim on Sondheim,” a 2010 Broadway revue commemorating his 80th birthday. He wrote the song in response to a 1994 headline in New York magazine that asked, “Is Stephen Sondheim God?” His musical answer: “You have to have something to believe in. Something to appropriate, emulate, overrate. Might as well be Stephen, or to use his nickname: God!”

That the works of this god have continued to be fruitful and multiply (barely a week goes by when I don’t receive notice of a new Sondheim revival or revue) partly stems from our deep reluctance to ever let him go. There’s a half-voiced fear among musical acolytes, understandable in a time in which theater itself is newly under siege, that on some level Stephen Sondheim represents the end of the line for a once-flourishing art form.

Contemporary composers like Lin-Manuel Miranda, Michael John LaChiusa, Adam Guettel, Michael R. Jackson and Jeanine Tesori have all been producing work of high caliber and originality. Yet none, with the qualified exception of Mr. Miranda, seem likely to engender the kind of enduring, passionate cult that Mr. Sondheim has inspired. Nor is it easy to imagine any of them ascending to the unapproachable dominance of their profession that was Mr. Sondheim’s for roughly half a century. His combination of sense (such ingenious rhymes, such intricate melodies) and sensibility (the aching ambivalence that always throbs beneath) remains ineluctably singular.