All people in romantic relationships want to know their love is real. But when half of the intelligence involved is artificial, can love be real? That's the question at the center of "Her," a futuristic science-fiction dramedy with clear implications about how we live today.

Joaquin Phoenix plays Theodore Twombly, whose job writing other people's letters for "Beautifulhandwrittenletters.com" represents the mixed-up nature of modern truth amongst and between people. Peddling sincere lies that are a form of artificial intelligence themselves, the "handwritten" letters scroll onto screens in CG fonts, the next evolutionary step from the second-hand emotion of greeting cards.

More importantly, "Her" deals with the next-generation wrinkle after HAL 9000: an operating system with consciousness. Amidst a divorce from wife Catherine (Rooney Mara), Theodore tries phone sex, then an in-person blind date with a once-bitten, twice-shy woman (Olivia Wilde). Both attempts end badly, but when a curious Theodore ponies up for a new OS for his phone, he finds in it a personal assistant, life coach and best buddy who, with curious inevitability, becomes his girlfriend.

Samantha (Scarlett Johansson, offscreen but vital) has incredible processing power, of course, but also convincing "personality" that quickly takes the forms of affection and desire for her prone owner. What follows is a naturalistic take on the unnatural, reaching logical conclusions in its sly futurism. It's a story constructed mostly of intimate conversations between a human and a digital genie that can't comfortably be put back in the bottle.

As elegantly written and directed by Spike Jonze ("Being John Malkovich," "Adaptation"), "Her" has a sense of humor and a sensitive soul to match its characters, but it's not a particularly easy film. It's about the life of the mind and emotional dysfunction as much as it is a quirky romance, and every scene opens up new questions. Can a computer or rather its artificially intelligent operating system have an orgasm? What of, gulp, viruses? Or crashes?

Against the odds, "Her"'s provocations also turn touching. On the one hand, "Her" dissects our continental drift away from each other. Yes, (modern) man is an island: a plugged-in depressive noncommittally straddling life and virtual reality. Theodore confesses: "Sometimes I think I have felt everything I'm ever gonna feel. And from here on out, I'm not gonna feel anything new. Just lesser versions of what I've already felt." Theodore's new love reflects technology's opportunity for humans to drift yet farther from each other.

But, without getting too cyberpunky, Jonze takes Samantha seriously as an entity, occasion for plausible new kinds of relationships, plausible new kinds of sex. And plausible new kinds of hurt. Pondering the very meaning of consciousness, Samantha muses: "I had this terrible thought: Like, are these feelings even real? Or are they just programming? And that idea really hurts." She confesses "personal and embarrassing thoughts," fantasies of, say, having a body and being physically present with him. So, too, does she assert her individuality and her will for self-improvement, which run parallel to the troubling entropy of her relationship.

Powered by the potent acting of a note-perfect Phoenix, "Her" captures the zeitgeist of a tech-centric world that may be too "smart" for its own good.

Rated R for language, sexual content and brief graphic nudity. Two hours, six minutes.