I’m becoming less sure that identity exists at all, beyond the trick of the light,” says Tilda Swinton. “What occurs to me is that identity is a matter of our personal choice, from minute to minute: that we are at liberty to transform — endlessly — at will.”

This porousness of identity hints at the many different changes the actress made along the way to being Tilda Swinton.

The daughter of a distinguished family whose pedigree reaches back 11 centuries into the Scottish Highlands, Swinton graduated from Cambridge with degrees in social and political science and English literature. She spent a period of her life as a performance artist (in a piece called “The Maybe,” she slept in a glass case for a week in galleries in London and Rome). For nine years, she served as muse to experimental filmmaker Derek Jarman, who taught her in turn, as she says, “…a way of performing in film without the traditional possibilities, something about presence and silence and not a lot about acting as such.”

That presence and silence charged the brief scene, bursting with subtext, that formed the gripping moral climax of “Michael Clayton,” for which she won an Oscar. The award was the latest in a slew of honors from BAFTA, the Hollywood Foreign Press Assn. and the Venice Film Fest. Her upcoming AFI tribute might be considered frosting on the cake.

“The range of her roles is so diverse,” says Rose Kuo, AFI’s artistic director. “She’s a kind of paradox. As a well-known movie star who regularly appears in big-budget movies, she can play psychological realism. But her background isn’t conventionally theatrical. It’s in esoteric art. In ‘Orlando,’ she not only demonstrated great affinity for a complex literary character, she radiated an onscreen androgyny and sophistication.”

Her face and figure suggest an abstemiousness that borders on the severe. But her height (5’10½”), red hair, sea-green eyes and skin that looks as if it retains moonlight lend her an ethereal presence, ideally suited to the White Witch she famously played in 2003’s “The Chronicles of Narnia.”

She’s also a fashion plate. Vanity Fair voted her one of its Best Dressed Women of 2007. As the subject of a 2003 Viktor & Rolf fashion show, she read from one of her poems that included the line, “There is only one you. Only one.”