The Matrix was, hands down, the best cyberpunk/kung fu/techno-pagan/Christian-allegory action film ever made. The Matrix Reloaded is the second best.

It is perhaps inevitable that the second film should have less power and impact than the first, which changed the rules of the movie universe in ways that the sequel can only expand upon, not surpass. The Matrix arrived stealthily and detonated without warning; Reloaded comes on a tsunami of hype and four years’ worth of fans’ expectations. The 1999 film offered beautifully choreographed action, innovative special effects, and a densely allusive narrative that provided endless fodder for graduate students; the second installment is less astonishing since it merely offers more of the same.

Of course, if you didn’t see the original, Reloaded will leave you not only astonished but thoroughly confused. As before, we’re back in the world of the Matrix, a virtual-reality simulacrum of late-20th-century Earth meant to hide from all humans the knowledge that they’re really bio-electric Duracells powering the machines that enslave them. Our hardy band of hackers — the messianic Neo (Keanu Reeves), his lover Trinity (Carrie-Anne Moss), his mentor Morpheus (Laurence Fishburne), and newbie Link (Harold Perrineau Jr.) — are among the soldiers fighting to save Zion, the underground refuge of the last band of free humans, from the latest onslaught by the machines, which have sent an army of squidlike robot sentinels tunneling toward the cave city.

Again, Neo enters the Matrix to consult the grandmotherly Oracle (Gloria Foster) for advice; again, Trinity and Morpheus wreak havoc in skyscrapers; again, Neo must confront Agent Smith (Hugo Weaving), an enforcement program who’s gone off the reservation but still has it in for his old foe. And again, Neo and his compatriots ponder the limits of free will in a universe where humans and computer programs are indistinguishable.

That’s a lot more brain exercising than most action films this side of The Terminator allow their audiences. Brothers Larry and Andy Wachowski, the writers and directors of the Matrix movies, are such philosophy geeks that they’ve given a cameo in this movie to Cornel West. In the first movie, they chewed over Emerson and James; this time it’s Schopenhauer and Nietzsche. (By the third installment, this November’s The Matrix Revolutions, it’ll probably be Camus and Sartre.) That makes for a lot of talking, especially in the expository first third, when Zion’s leaders debate what to do about the burrowing machine army. It’s a section that devoted fans (and those who enjoyed the two latter-day Star Wars movies) will love, but it may leave more-general viewers counting the minutes until the action sequences.

Which are pretty damn cool. A sequence the filmmakers call the ‘‘Burly Brawl,’’ where Neo battles Smith and 99 of his clones, is as gracefully executed as anything in Crouching Tiger, Hidden Dragon. (That film, like the Matrix movies, has fight choreography by the Hong Kong master Yuen Wo-ping.) There are the Twins (Neil and Adrian Rayment), two powder-faced baddies who can turn into ghosts and pass through matter. And there’s a 14-minute freeway chase involving cars, motorbikes, semis, and a samurai sword. All this involves special effects that are, in their own way, as cutting-edge as the much-copied ‘‘bullet time’’ technique from the first film, if subtler in appearance.

If Reloaded doesn’t necessarily change the rules of filmmaking the way its predecessor did, it certainly changes its own narrative rules in a classic middle-film-of-a-trilogy way, like The Empire Strikes Back, or The Lord of the Rings: The Two Towers. There are some plot shockers that raise questions about what Neo’s crew (and viewers) think they know about the Oracle, her prophecies, the natures of both the Matrix and the rebellion, and Neo’s own anomalous gifts. There’s enough to chew on here for repeated viewings, though the questions will probably remain unanswerable until we see Revolutions. Even then, one mystery will probably remain: as in the first movie, the wild card is something beyond the reasoning of both computers and humans — the inexplicably transcendent power of love. That may be the greatest astonishment the film has to offer — or, as the philosopher Keanu Reeves would say, ‘‘Whoa.’’