Fighters don't lie. They rationalize, then they change their minds. Consider Bernard Hopkins an expert.

The former undisputed middleweight champion of the world really did mean it when he told his hometown of Philadelphia and the boxing world that he was going to retire back in 2005. At age 40, he said he was fulfilling a long-held commitment he'd made to his late mother, Shirley. He wasn't lying when he promised her she'd never witness him beaten and battered, so punch drunk from so many blows that he'd resemble a zombie.

Then Hopkins rationalized, of course. He surveyed the boxing landscape and saw the stiffs. He realized all his faculties were still in order, and the paydays were there to be had. And then Hopkins did what any fighter of his caliber with sense does today: He went for the money.

He's still doing it now, at age 46. Considering the kind of dollars a fight like Floyd Mayweather Jr. vs. Sugar Shane Mosley will generate, can you really blame him? Even if it means breaking a promise to Momma Hopkins?

"Fighters who can really fight continue to fight," Hopkins (51-5-1-1, 32 KOs) explained Wednesday, en route to Vegas for Saturday night's festivities. "We know what I can do . . . what I've done. When my momma made me promise I wouldn't fight past age 40, what she was saying was to promise her - and I mean no disrespect here - that I wouldn't walk around looking like Joe Frazier.

"Let's keep it real. There are no success stories in the boxing game coming out of Philadelphia other than Bernard Hopkins," he continued, usually talking of himself in the third person. "Frazier's legacy over the last few years has not been good. So when my mom said what she said, she was being concerned for her son. If she was here now, seeing how how healthy I am, how good I still am and how I have the chance to finally earn the money that was denied to me years ago, she'd support me."

Actually, it depends.

If Hopkins were fighting a technician like Mayweather, Momma Hopkins may not have had a problem with it. Watching your son potentially get outclassed with pitty-pat shots, garnering the occasional bruise and nothing else, is something most parents can stomach. Particularly when millions are earned because of it.

But when you hear rumors Hopkins put out there himself - that a perennial middleweight like himself is looking to move up to the heavyweight division to fight a young, powerful stud like David Haye - worries kick in.

Such a fight would be stupidity. The next thing we'd all look for is slurred speech, and slower, staggering walks.

Essentially, another version of Tommy "Hit Man" Hearns, or, worse, Meldrick Taylor.

"I'd love to disagree with you, but I can't," said Hopkins' longtime trainer, Nazeem Richardson, moonlighting as Mosley's trainer this Saturday night in Vegas. "I've told Bernard that, myself. There's a lot of cats out here he can take. Even now, especially in the middleweight and light-heavyweight division. But he knows how I feel about him moving up to fight a big boy like Haye. I would not advise that."

Neither would Hopkins. The problem is that Hopkins sees the money being generated elsewhere, wondering why a chunkier piece of the action isn't flowing in his direction.

Hopkins' trepidation is understandable, of course, when you knock out Oscar De La Hoya and end up on the Tonight Show with Jay Leno back in 2004, you should get paid. When you school a young knockout artist like Kelly Pavlik back in October 2008, you shouldn't have to sit around for 14 months, while the birth certificate collects dust, waiting for your next fight. Particularly when you're a promoter for Golden Boy Promotions.

"People don't understand I can still fight because I'm a late bloomer," Hopkins explained. "I take care of myself. I don't run around on the streets. I don't run around with 20-or-30 different women. I've been married for 17 years. I live a good lifestyle. I work out and train all the time, just for recreation, alone. I haven't eaten a steak in two decades. The only thing that's ever stopped me is the politics of boxing. But I'm still here."

Perhaps the next step could be a rematch vs. Joe Calzaghe, or a match vs. super-middleweight Lucian Bute. With Hopkins, it's about the check, winning, and his legacy.

"Momma would approve," he deadpans. "Believe me."

Who knows? She just might. Even if it's while her son is sounding a lot like Mayweather, Jr.

Contact columnist Stephen A. Smith at 215-854-5846 or ssmith@phillynews.com.