When HAL starts to go haywire during the mission, he becomes a classic Kubrickian character: violent, desperate and suddenly willing to sacrifice any last semblance of order in the name of survival -- which, ironically, is not to be. This portion of the film concludes with Bowman slowly killing HAL by disconnecting his circuitry after HAL has murdered every other member of the crew. In this memorable sequence, HAL's singing of the children's song "Daisy" becomes progressively slower and slower. We've learned to play God, but our celestial Garden of Eden has turned out even worse than the one in the Book of Genesis. HAL's death -- essentially the mere unplugging of a computer -- is easily the most moving scene of the movie.

Which brings us to the film's famously abstract coda, "Jupiter and Beyond the Infinite." As Kubrick's relatively straightforward narrative gives way to a series of kaleidoscopic images, Bowman is transported into the realm of the mysterious, godlike aliens, who have seemingly guided human evolution for 4 million years. That said, everything in this final portion of the movie is open to debate. What we do know for sure is that although Kubrick and Clarke toyed with the idea, we never actually see the aliens, which is perhaps the best decision made in "2001: A Space Odyssey." Sci-fi aliens that we do see in cinema are almost always a disappointment; they rob us of our imagination -- something Kubrick never lets happen in this film.

Hiding the aliens from view also allows Kubrick to extend the notion of "2001" as a modern-day creation fable. The film contains several allusions to the ancient Greek myth of Prometheus, who gave men the use of fire only to see them lose control of its power. Moreover, the astronauts' ultimate destination, Jupiter, is also the Roman name for Zeus, the god of all gods. As the now unmanned Discovery arrives in Jupiter's orbit and Bowman is taken into the alien realm, a higher power has helped us continue forward in spite of ourselves.

Next we see Bowman, now an old man, living out his old age like a zoo attraction in a feigned Louis XVI-style bedroom, assumedly created for him by the aliens. And then suddenly the creation theme continues as a giant fetus inexplicably rises over Earth. Although birthdays have noticeably been happening in the background all along (Poole, Floyd's daughter), all bets are off as to the movie's ultimate statement. At the film's Hollywood premier in 1968, Rock Hudson walked out saying, "Will someone tell me what the hell this is about?"

There's no easy answer to that question -- and yet that is decidedly a strength, not a weakness. In a feat that becomes all the more astonishing with each passing year of banal blockbusters, Kubrick -- at the peak of his commercial and creative success, after "Spartacus," "Lolita" and "Strangelove" -- convinced a major Hollywood studio to back what is essentially a piece of avant-garde filmmaking. He devoted the last half-hour of "2001" to an unexplainable series of dialogue-free images, and audiences loved it. The movie was the third-highest grossing of 1968, after "The Graduate" and "Funny Girl." Perhaps some of those moviegoers didn't take the movie as seriously as scholars and movie geeks might now, viewing it as merely as a pre-Omnimax and MTV music video -- something far-out to get stoned and see. But that such a challenging and ambiguous film captured the national (and international) consciousness is a victory to all of us who believe that strictly narrative filmmaking maintains a stranglehold on popular cinema.

"Movies present the opportunity to convey complex concepts and abstractions without the traditional reliance on words," Kubrick told interviewer Joseph Gelmis in 1969. "I think that '2001,' like music, succeeds in short-circuiting the rigid surface cultural blocks that shackle our consciousness to narrowly limited areas of experience and is able to cut directly through to areas of emotional comprehension." In other words, some have accused Kubrick's film of being too cold and abstract to register with viewers in more than an intellectual way -- but they're wrong. The nonverbal storytelling and eventual delving into abstraction constitute a refusal to spoon-feed the audience ideas.

Despite the wide scope of interpretation "2001" allows, there's something oddly unifying at work here. Enriching and vital as human diversity is, there's a transcendent power in the idea of our having a larger purpose, the chance to be freed from the divisions and diversions of daily life with a guiding hand behind us. If that's not something to get emotional about, what is?