Imagine having no talent. Imagine being no good at all at something and doing it anyway. Then, after nine years, failing at it and giving it up in disgust and moving to Englewood, N.J., and selling aluminum siding. And then, years later, trying the thing again, though it wrecks your marriage, and failing again. And eventually making a meticulous study of the thing and figuring out that, by eliminating every extraneous element, you could isolate what makes it work and just do that. And then, after becoming better at it than anyone who had ever done it, realizing that maybe you didn’t need the talent. That maybe its absence was a gift.

These were the stations on the via dolorosa of Jacob Cohen, a.k.a. Rodney Dangerfield, whose comedy I hold above all others’. At his peak — look on YouTube for any set he did between 1976 and 1990 — he was the funniest entertainer ever. That peak was long in coming; by the time he perfected his act, he was nearly 60. But everything about Dangerfield was weird. While other comedians of that era made their names in television and film, Dangerfield made his with stand-up. It was a stand-up as dated as he was: He stood on stage stock-still in a rumpled black suit and shiny red tie and told a succession of diamond-hard one-liners.

The one-liners were impeccable, unimprovable. Dangerfield spent years on them; he once told an interviewer that it took him three months to work up six minutes of material for a talk-show appearance. If there’s art about life and art about art, Dangerfield’s comedy was the latter — he was the supreme formalist. Lacking inborn ability, he studied the moving parts of a joke with an engineer’s rigor. And so Dangerfield, who told audiences that as a child he was so ugly that his mother fed him with a slingshot, became the leading semiotician of postwar American comedy. How someone can watch him with anything short of wonder is beyond me.

“To be a comedian,” he said, “you have to get onstage and find out if you’re funny.” He wasn’t. During his first career, performing as Jack Roy, he was a singing waiter, used props, tried impressions. Even after his second coming — using a stage name devised by a club owner as a gag — and becoming a regular on “The Ed Sullivan Show,” he could be miserable. In a YouTube clip of him performing on “Sullivan” in 1969, Dangerfield’s face is the unsettling bluish-pink of raw chicken. The jokes — about getting directions, his wife’s driving, their apartment — keep bombing. The setups are too long; the delivery is too slow; the punch lines are so lame that you can hear the scattered laughter of distinct individuals. Even worse, he panders. “I’ll tell you, it’s nice to hear you laugh,” he says at one point. It’s almost unseemly.