Historically, science-fiction films have come in two varieties: one driven by ideas, the other by gadgets, gimmicks, and bug-eyed monsters. The former type has mostly been in retreat for years, if not since its apotheosis, Stanley Kubrick's 2001: A Space Odyssey. But A.I.—a realization of a long-discussed, never-realized Kubrick project, written and directed by Steven Spielberg—has enough ideas to make up for the extended shortage. Working with wild ambition that occasionally (and inevitably) overwhelms itself, Spielberg launches an inquiry into humanity itself, its origins, its nature, and its end. His vehicle is a robotic boy created by scientist William Hurt and played by Haley Joel Osment, a machine that, unlike any before him, comes programmed to love his adoptive parents. Much has been made of the incompatibility between Spielberg's sentimentality and Kubrick's chilly sensibility, but that broad generalization overlooks the counterbalances built into both directors' work. Spielberg's films often use sentiment to keep overwhelming darkness at bay, while Kubrick's chilliness is frequently paired with a kind of tough-minded humanism. Stylistically, the directors have as many similarities as differences. Few other filmmakers can wring so much out of a single image, and few are as adept at allowing their imagery to speak for itself. In the initial segments of the episodic A.I., Spielberg seems to take his cues from the Kubrick of Lolita, The Shining, and Eyes Wide Shut, presenting a family dynamic whose eerie underpinnings suggest how readily it could take a disastrous turn. A.I. is seldom more assured than in these early sequences, but it's tough to argue with Spielberg's decision, natural to the Pinocchio-inspired story, to send Osment out into the world for firsthand encounters with his society's hostility to artificial beings. Spielberg continually redefines his film, each episode offering new variations on Osment's central quest for meaning itself, albeit in a form his programming allows him to understand. The director attempts to serve up a heady mixture of science, fairy tale, philosophy, psychology, and religion, and his attempt to make it palatable occasionally gets in the way of the actual film. Ben Kingsley's narration, which opens A.I. and bookends its final segment, is intrusive, distracting, and unnecessary, as are the occasional characters who explain developments that were already clear or better served by slight opacity. But, as with the prologue and epilogue of Saving Private Ryan, it's not the film's obvious flaws that linger, but the delicacy of its virtues, from the difficult performances of Osment, Jude Law, and an expressive teddy bear to the understated believability of a futuristic coffeemaker. Kubrick would have made a different film, but discussing the hows and wherefores is as pointless as debating whether his version would have been better. Spielberg's best tribute to 2001's director is this: With A.I., he has created what history should confirm as one of the defining films of its time, a compelling, moving inquiry into the most basic elements of existence, told with fear and awe in a vocabulary exclusive to moviemaking.