We go to movies not just to escape, but to discover. We might identify with the cowboy or the runaway bride or the kid who befriends a creature from another planet.

To see yourself on screen has long been another way of knowing you exist.

Sidney Poitier, who died Thursday at 94, was the rare performer who really did change lives, who embodied possibilities once absent from the movies. His impact was as profound as Method acting or digital technology, his story inseparable from the story of the country he emigrated to as a teenager.

“What emerges on the screen reminds people of something in themselves, because I’m so many different things,” he wrote in his memoir “The Measure of a Man,” published in 2000. “I’m a network of primal feelings, instinctive emotions that have been wrestled with so long they’re automatic.”

Poitier made Hollywood history, by breaking from the stereotypes of bug-eyed entertainers, and American history, by appearing in films during the 1950s and 1960s that paralleled the growth of the civil rights movement. As segregation laws were challenged and fell, Poitier was the performer to whom a cautious Hollywood turned for stories of progress, a bridge to the growing candor and variety of Black filmmaking today.