Floyd Mayweather has a favorite saying that he has brandished in recent years when asserting his status as the best pound-for-pound boxer of all time: "Women lie, men lie, numbers don't lie." It's a direct reference to Mayweather's perfect record, which is now 47-0 with 26 knockouts.

It's a meaningless utterance, though. Of course numbers "don't lie." But by themselves, they also don't win arguments.

Numbers can be effective tools to build an argument around, but they have no significance divorced from their context.

Mayweather's undefeated record is an impressive accomplishment to be sure. To compete and win at the championship level for nearly two decades is remarkable. It was remarkable when Rocky Marciano and Joe Calzaghe retired as undefeated champions, as well.

But neither Marciano nor Calzaghe is often mentioned in debates over the all-time, pound-for-pound elite.

Mayweather has a better resume than both Marciano and Calzaghe, and he has generally looked more impressive in compiling it. If Mayweather can get by Manny Pacquiao on May 2—and I'm already on record predicting that he will—he will most likely retire undefeated.

If he does it, I'll consider him the best unbeaten fighter of all time. And win or lose, he's a first-ballot Hall of Famer. No matter what happens on May 2, Mayweather is among the all-time greats. 

If Mayweather can take care of business against Pacquiao, the other great star of his era, and retire undefeated, it will rank among the greatest boxing accomplishments of all time. But whether it will be the greatest boxing accomplishment in history and enough to establish Mayweather as the best ever will still remain open for debate.

Since the dawn of the gloved era in the late 1800s, the great sport of boxing has been full of remarkable achievements by great ring warriors. And the greatest achievements of all time have been events that occurred within historical contexts that made them possible.

They are the combination of remarkable fighters and unique circumstances.

One of the greatest pound-for-pound punchers ever, Bob Fitzsimmons was history's first three-division world champion and knocked out heavyweights who outweighed him by 40 or more pounds.

Joe Gans was lightweight champion in the early 20th century. The first African-American to hold a world title in boxing, he was an innovator and hailed by his contemporaries of all races as the "Old Master."

For a brief period of time in 1938, Henry Armstrong held the world title at featherweight, lightweight and welterweight simultaneously. It was an era when there was only one world title and only eight weight classes. As many as 20 different fighters might claim world-champion status over that same span of weight in our current, alphabet-soup era.

Armstrong also challenged for the middleweight title against Ceferino Garcia in 1940 and came up just short, earning only a draw. He came tantalizingly close to holding half of the available world titles. 

After losing to Hall of Famer Jake LaMotta in his 41st fight in 1943, Sugar Ray Robinson went eight years and over 90 fights without losing again, collecting first the welterweight and then the middleweight titles.

In 1951, Robinson finally lost to Hall of Famer Randy Turpin. But he knocked Turpin out two months later in the rematch, then beat Hall of Famers Bobo Olson and Rocky Graziano, before passing out with heat stroke when he was far ahead of light heavyweight champion Joey Maxim.

Robinson then retired for three years, came back in 1955, and held the middleweight title three more times.

Roberto Duran spent the 1970s establishing himself as the greatest lightweight to ever live, then went up to welterweight and beat pound-for-pound great Sugar Ray Leonard. He would eventually win a world title at middleweight when he was 37.

A list like this could go on for many more paragraphs. Boxing is a sport with a long, rich history, and Floyd Mayweather is an important part of it. 

If you want to bandy Mayweather about as your pick for the greatest who ever did it, you are well within your rights as a boxing fan to do so. 

Just don't point at his record as irrefutable proof. It can only be a piece of an argument—and it's an argument that can never be ultimately decided. 

Follow Briggs Seekins on Twitter at @Briggsfighttalk and check out his blog, Pioneers of Boxing, to read about the early, bare-knuckle days of the sport.