“Knowing is not my business. Not knowing is,” Polish director Krzysztof Kieslowski once said in “I’m So-So,” a documentary about his life and work. “What if?” “Why not?” “How come?” – these were the questions that Kieslowski explored, in documentaries and fictions (both realistic and fabulistic), over the course of a 30-year career, which was brought to a temporary end by a self-imposed retirement in 1994 and a final one in 1996, when, at the age of 54, he went in for heart surgery and never woke up.

As a boy, Kieslowski dreamed of becoming a stoker. His father, who died of tuberculosis when Kieslowski was a young man, suggested fireman’s training instead. But he didn’t like it and decided he wanted to be a stage director. He would study film to gain entrance to the theater. After being rejected twice, he was finally admitted to the Lodz Film School.

In “I’m So-So,” Kieslowski talks about his own documentary films, which he made from the 1960s to the 1980s. He calls them mini-observations about life in Poland. And he warns against any society in which the lives of everyday people – to use his own examples: students, office workers, bricklayers, miners, soldiers, lawyers, undertakers, race-car drivers, doormen, doctors, and patients – are not described accurately and with empathy. Without these descriptions to counter the propaganda, he says, people are all alone; we are lost. In 1980’s “Talking Heads” (April 17-18), a 16-minute short of man-on-the-street interviews, Kieslowski asks 40 Polish cit izens – from the young to the old – who they are and what they want, and everyone, with the excusable exceptions of the baby and the drunken engineer, responds in kind: What they want is freedom.

“The Decalogue” (April 11-23) – 10 hour-long films, each of which considers one or more of the Ten Commandments – was made for Polish television in 1988, and is his masterpiece. Like the best short-story writers, Kieslowski, along with longtime collaborator Krzysztof Piesiewicz, establishes his premise and then teases out its variations and contradictions; he is equally skilled at building tension and releasing information at precisely the right moment.

With “The Double Life of Veronique” (April 5, 15, 17 & 18) and his “Colors Trilogy” (April 9-10, 16-19 & 23), Kieslowski returned to the kind of metaphysical fantasies he previously played with in 1987’s “Blind Chance” (April 8, 14, 15 & 19) and 1984’s “No Exit,” though with varying degrees of success. If, as he once said, every one of his films is autobiographical in some way, then, from “Camera Buff” (April 7 & 12) to “Veronique” to the trilogy of “Blue,” “White,” and “Red,” Kieslowski charted his own development for us – from obsessed chronicler to benevolent puppet master to a lonely old judge who eavesdrops on his neighbors.

But the Film Society’s declaration, somewhat oddly, that its retrospective marks the 10-year anniversary of Kieslowski’s death, reminds me of the opening line from a story by Leonard Michaels: “In 1980, Raphael Nachman, a visiting lecturer in mathematics at the university in Cracow, declined the tour of Auschwitz, where his grandparents had died, and asked instead for a tour of the ghetto, where they had lived.”

Until April 23 (70 Lincoln Center Plaza, 212-875-5601).