LAS VEGAS -- Manny Pacquiao is an enormous little man, the world's smallest giant. His power begins in his softball-sized calves and emanates upward, ultimately finding freedom through his fists. When you watch him set his feet and throw his hands like bludgeons over the course of a 12-round fight, it begins to look like something other than human, like an incinerator, or an engine.

There will be endless odes written to the fact that Pacquiao is 40 years old and boxed at least 10 years younger Saturday night in his split-decision victory over Keith Thurman for the WBA world welterweight title at the MGM Grand Garden Arena. That much is true; he has spent the past three fights revising the athlete's bell curve, picking up the odds and ends -- power, stamina, interest -- he had seemingly lost along the way.

But the emphasis on Pacquiao's age obscures the most remarkable aspect of his current iteration: He can make a punishing, brutal enterprise look joyous. He is the entire conflicting boxing experience, its visceral beauty and intellectual revulsion, embodied in one person.

There was nothing easy about this fight. Thurman, undefeated in 29 fights before Saturday night, was strong and proud and resilient in ways that may have surprised even himself. Pacquiao advanced like an invading force for 12 rounds, charging and prodding and then firing himself at Thurman with superhuman energy. Thurman, whose face was blotchy and bleeding before the end of the first round, didn't know what to make of it; there's no chance he'd ever experienced this form of relentlessness. He was in the ring with a guy fighting for something nobody else can see.

Pacquiao loves this, probably more than he should. He responded to every heavy Thurman punch by smiling and slapping his ears with his gloves, as if to shove everything back into place. Before nearly every one of the 12 rounds, he stood at the center of the ring, waiting for Thurman to arrive, as if to remind his 30-year-old opponent that he was facing a man whose endurance is at odds with his age. During the rare breaks in flurries, he summoned Thurman toward him, begging for more exchanges.

It is this last point that is willfully dangerous and admittedly fascinating. Pacquiao, along with his ability to inflict punishment, exudes a masochistic streak. He likes a bloody fight as much as the fans, and that's the one quality that has made him the most riveting fighter of his generation.

This was never more evident than midway through the 11th round, when nearly everyone in the arena -- except judge Glenn Feldman, who upheld boxing's penchant for weirdness by scoring the fight for Thurman -- believed Thurman's only chance was to knock out Pacquiao. Imagine Floyd Mayweather in this situation; he would dance and duck for the final 4½ minutes of the fight, the crowd be damned. He would win, but it would be deemed hollow, somehow less than. Pacquiao is different. He kept pushing forward, intent on fulfilling his prediction of a knockout. There was just a small chance he could lose the fight, and yet he couldn't help himself. He took the chance, because there is something inside him that tells him he must.

(Mayweather was ringside, of course, still accompanied by his merry band, wearing a floral-print dinner jacket that probably cost as much as the annual budget of a midsize city.)

Why does Pacquiao continue to fight at 40? Because he can, is one reason, but the deeper answer seems to lie in those final minutes of the fight, when the fans chant his name just a little bit louder and he gets pulled into the momentum.

He was asked after the fight whether nights like this one make him consider the long-term cognitive damage at stake. (The question was framed around his second job as a senator in the Philippines, a gig that calls for him to rely on his brain.) He took a massive number of hard shots -- 192 power punches, the most Pac has taken in the 43 fights he's had since they started the CompuBox stats -- from Thurman, whose heavy hands Pacquiao compared to the notoriously heavy-handed Antonio Margarito. And at this point there's no way of calculating the cumulative toll of 24 years and 71 fights as a professional boxer.

This issue is never welcome in boxing, especially amid the warm afterglow of a huge moment, and Pacquiao is the master at pretending this particular question either doesn't require a direct answer or doesn't pertain to him.

"Your question is when am I going to retire," Pacquiao said, reframing the question to fit his needs. "I can still fight. I can give a good fight and entertain the fans. The ability I have is not my own. God gave me this ability to continue. I believe I am here to inspire the fans and be a role model to everyone as a follower of God the Lord Jesus Christ."

What is worth it? How much money and attention is enough to not only accept the risk but taunt it? Pacquiao, victorious, sat at the postfight podium wearing sunglasses and a white jacket. A private jet destined for Manila waited a few miles away. Second thoughts were the last things on his mind. There are hints that he may feel immune from the dangers of his profession, somehow inoculated by a higher power.

He is 40 years old, and he remains determined to keep asking the question that nobody can answer: How many times can a career be defined?