A filmmaker as cerebral as Manoel de Oliveira risks becoming so enamored of his own metaphysical speculations that he abandons his audience to frolic in his own private garden of intellectual delights. And in ''The Uncertainty Principle,'' his eighth movie to be shown in the New York Film Festival, this 93-year-old Portuguese director goes where only a few cult admirers are likely to follow.

The pivotal character, Camila (Leonor Baldaque), is a proud, idealistic young woman who regularly prays to a statue of Joan of Arc. As her marriage to a childhood friend sours, the movie poses oblique questions about the interplay of morality and intelligence in the development of Western culture.

Based on Augustina Bessa-Luis's novel ''The Family Jewel,'' ''The Uncertainty Principle'' has a melodramatic plot that sounds much juicier than it plays out on the screen, as the accumulated betrayals and reversals build toward one character's death by arson in a discothèque fire. The story focuses on Camila's complicated relationships with Antonio (Ivo Canelas) and José (Ricardo Trepa), childhood friends from different social classes, who were brought up as brothers.