"There's a light in this world, a healing spirit more powerful than any darkness we may encounter," begins Sir Richard Attenborough's narration to this documentary. By the time it ends, even the most cynical viewer might agree with him. The documentary, which premiered theatrically in 1986, was produced, written and directed by sisters Ann and Jeanette Petrie. (Ann is a former ABC-TV producer, Jeanette, a real estate executive.) In some ways the profile is disappointing. For instance, Mother Teresa never talks about herself. Nobody would expect her to say she'd like to take a few days off for a trip to Vegas, but it would be enlightening to hear her answer such a question as "Have you ever regretted not having lived a more traditional life and been a wife or mother?" There is however a brief section on Mother Teresa's early life as a young, pretty girl in what was then Albania. She was, says a niece, known as a mischievous child, and the Petries make good use of her sense of humor. They also suggest that Mother Teresa is no slouch in the toughness department. A Red Cross worker in Beirut, recalling her visit there in 1982, says, "We were running out of just about everything. A saint was not what I needed most." Mother Teresa however is a hands-on sort of saint, and she appears stubborn, not sanctimonious, in meeting a priest who tries vainly to dissuade her from crossing the battle-torn city. The Petries don't shrink from showing the deformed, the dying or the dead, which increases the tape's impact. This also illustrates a Mother Teresa comment: "You can find Calcutta all over the world if you have eyes to see." (Today Home Entertainment, $59.95)