"I think my open and uncynical attitude toward life will enforce a sense of freedom in my child. that's very important." Photo by Michael Grecco

That might be because she is now, at 26, the mother of a toddler -- 16-month-old Mia, who accompanies her mom to film sets. When Winslet isn't working, her typical day is getting up with Mia at 7:30 a.m., playing with her, taking her to baby gym or swim class or music lessons or for a walk, putting her to bed, then maybe reading scripts or having dinner with friends. That's also how she describes a perfect day. (Recently divorced from Mia's father, Jim Threapleton, Winslet is now dating "American Beauty" director Sam Mendes.)

Or it might be that her conscious memory begins, predictively and aptly, at a point of creativity. Winslet's performance in her new movie, "Iris," in which she plays the young Iris Murdoch, sets up, in flashback sequences, Judi Dench's portrayal of the novelist, philosopher and critic later in life, when she was stricken with Alzheimer's disease. The role has placed Winslet on several year-end critics' association honors lists. (She and Judi Dench have been Oscar nominated for "Iris".)

Winslet has been acting in one way or another since childhood. Her first professional acting role, at 12, was in a commercial for a breakfast cereal called Sugar Puffs. "I danced around behind the Honey Monster with a lot of other kids," she says. "But it was dancing along to no music because they had to get the dialogue of the Honey Monster clean. So we were probably all out of time, and I'm sure that I was on the edge and very probably not seen." Her first feature film was 1994's "Heavenly Creatures," directed by Peter Jackson. Her acclaimed performance led to her being cast as Marianne Dashwood in Ang Lee's "Sense and Sensibility" (1995), for which she was nominated for an Academy Award, pretty much sealing the deal on her professional future. But if, for some reason, she had not been able to earn her keep as an actress, Winslet believes she would have acted anyway.

"I never thought, 'I'm going to do that and be really successful,' " she says. "I thought, 'That's what I will love to do the most.' " Had the acting thing not panned out, she might have earned a living as a makeup artist. "Not because I'm obsessed with makeup or even particularly wear much. But, you know, painting faces -- I've always loved it. Because it's intimate, isn't it? You should ask my sisters. I was always coming at them with makeup or trying to cut their hair."

Winslet grew up in Reading, an old market town about an hour outside of London, in what one article about her characterizes as "a theatrical family." When it is pointed out that this adjective suggests a family in which everyone was smiting his or her brow and emoting at the dinner table -- If you don't pass me the peas, I shall die, forsooth -- rather than simply a family of actors, she replies: "Oh, well, it was probably both of those things. An acting and a theatrical family. My family is definitely larger than life. When everybody, pretty much, in your family is an actor, how can you not get theatrical from time to time? And that was nothing but absolute fun."

Sitting on a sofa in the Dorchester hotel in London, the city where she now lives, Winslet positively radiates energy. That would not raise the collective eyebrows of the everyone-on-Earth who saw "Titanic," for which Winslet earned her second Oscar nomination. ("A part of me," she says, "is still going, 'Blimey, I was in that film!' ") As Richard Eyre, who directed Winslet in "Iris," observes, she radiates energy even when swimming around in muddy water, naked, while being directed third-hand. Of her underwater acting abilities, also on display in "Titanic" and in a small way in last winter's "Quills," in which her character ultimately drowns in an 18th-century laundry vat, Winslet says: "I've perfected them by now, haven't I? It's like, 'Also does water.' "

"There are actresses who have a sort of celebrity and a kind of glow about them but who aren't real actors and are always the same," Eyre says. "And some of them are charming. But Kate is a really, really good actress. She has a real ability to get inside the part, to change herself from role to role."

In person, Winslet has a voice that deserves to be heard, not rendered on the page; it's equal parts feeling and intelligence. "She's sort of a heat-seeking device," Eyre says. "You can always find Kate in a crowd. But what she's also got, and what's so attractive, is her intelligence. You know, that's what's sexy."

Winslet speaks quickly, at almost a screwball-comedy rate, although earthy where screwball heroines are airy, and with a range of tones and emphases that, in print, can only be indicated, in pale imitation, by italics: "I really want to watch "Heavenly Creatures" again. God, it was nine years ago. A-mazing, too, that I just got on the plane and went to New Zealand on my own at the age of 17. It's bizarre. And at the time, I was thinking [her voice drops to a whisper]: 'This is so exciting! How is this happening?' " Her voice returns to normal speaking tones. "But I just loved it. When you're a young actress, there is something incredibly raw there; you don't know what something's going to look like, whether you're achieving the desired effect. Maybe I know too much now. And whether that's a good thing or a bad thing ... maybe it's just a thing. But I'm certainly aware of how unaware I was."

At first, she was daunted by the prospect of playing Murdoch, who died in 1999: "I was going, 'How can I play Iris Murdoch? She's far more intelligent than me." But Winslet may be closer to the character than she thinks. Characterizing Murdoch's books for the British newspaper "The Guardian," novelist Martin Amis refers to their "wild generosity, their extreme innocence and skittishness, their worrying unpredictability." Describing what the Irish-English writer brought to her work, he notes: "Her world is ignited by belief. She believes in everything: true love ... magic, monsters, pagan spirits." That serves, in a way, as a summary of the qualities of Winslet's work and what she brings to it as well.

"It's probably true that there were a few emotional similarities between myself and Iris," she concedes. "In the sense that she absolutely lived her life to the full ... especially having a child and wanting to give her as much of myself as I can, now, when [Mia] is so little. The things she experiences now -- how she chooses to play and dance -- these are all things she's forming in herself. And yet, she will always take things from her parents. And those things will form who she is as well. I think my open and relatively uncynical attitude toward life will in some way enforce a sense of freedom in Mia, in my child. And that's very important."

Her sense of freedom, her unself-consciousness about nudity when the role calls for it and her untroubled non-conformity with the stick-thin Hollywood ideal are, along with "Titanic," the most frequently referenced topics when Winslet's name is raised. Along with her ability to shed inhibitions, both Eyre and Alan Parker, who directs Winslet in the upcoming movie "The Life of David Gale," praise her dedication to technique and her sense of what will work in a shot. "I asked her to work hard on the [American] accent," Parker says. "Before shooting, we had a call from Kate's agent's office. The girl on the phone sounded like the usual officious, demanding New York assistant that American agents attract. In fact, it was Kate trying out her accent and fooling everybody."

At the moment, with "David Gale" in the can and "Iris" just out, Winslet is focused on being there for Mia: "I've always left big blocks of time to decompress a little bit and wipe the slate clean and have life. [She claps her hands to emphasize the point.] I couldn't do it if I was exhausted, or if I was still carrying the little threads of the character I'd just played. I like to leave a bit of breathing space. It's important to have life as an actor. Because it's where you get your stuff from."