Bernard Hopkins summons up statistics sheets to prove his point.

Carlos Monzon and Marvin Hagler each insist they did it in much more difficult eras.

Harry Greb will thumb you in the eye and steal your wife for suggesting anything other.

And Sugar Ray Robinson is sure it is sacrilege for any serious judge of boxing history to come out against him.

But just who is the greatest middleweight boxer of all time?

The question has raised itself again this week as Hopkins prepares to defend a version of the world crown for the 20th time against Howard Eastman next Saturday night.

Hopkins' current record of 19 successful defences of major versions of the world title have long since surpassed the record of 14 previously held by Monzon.

On Saturday night in Los Angeles he believes he will make a new mark in the history books which will convince future generations of his all-time greatness.

But for now at least, Hopkins is denied the universal acclaim he believes he is due because some question the quality of the opponents he has beaten.

Only Oscar De La Hoya and perhaps Felix Trinidad are destined to one day join Hopkins in the Hall of Fame, and the 'Golden Boy' was never more than a welterweight great who stretched himself so far.

Monzon, meanwhile, can point to a seven-year undefeated reign as champion during which he overcame three fellow Hall of Fame fighters in Nino Benvenuti and Emile Griffith, both twice, and Jose Napoles.

Monzon, who was imperious at his peak, also overcame top-quality challengers like Rodrigo Valdez and the big-punching Bennie Briscoe before retiring as undisputed champion in 1977.

Hagler - third only to Hopkins and Monzon with 12 successful defences to his name, has a case for coming through even greater tests against the likes of Roberto Duran, Thomas Hearns and John Mugabe.

Hagler's icy detachment enabled him to cut through the glamour of his period as champion, and when he felt he had been robbed he simply turned his back and walked away.

After five years as world welterweight champion, Sugar Ray Robinson went on to hold the middleweight crown five times throughout the 1950s.

His great battles with the likes of Jake La Motta, Rocky Graziano and Carmen Basilio each represent milestones in boxing history, but with so many title losses also to his name, did Robinson's true legend remain at welterweight?

Harry Greb was a fast-living, foul-filled freak who reigned as middleweight king for three tumultuous years from 1923 to 1926.

Greb endured bloody battles against the likes of Mickey Walker and Tiger Flowers but was best known for an audacious non-title win over future heavyweight champion Gene Tunney in 1922.

Greb died prematurely on the operating table in 1926 whilst undergoing facial surgery following a car accident.

It was posthumously revealed that Greb had fought for the last five years of his career without sight in one eye.

So who was the greatest? The arguments will rage on and on until a time machine is invented and the champions of history can battle it out for themselves.

There is no formula for establishing the undisputed champion of all time and every boxing fan has his own opinions on what constitutes such greatness.

But natural talent, longevity and the quality of his opponents are the three most common attributes associated with personal views which are bound to be castigated and championed in equal measure.

So it is with great timidity that this column elevates Monzon to the lofty pedestal of the greatest middleweight ever.

Monzon reigned over a fine era of fighters with apparent invincibility, until a taste of the canvas in his ultimately successful defence against Valdez in 1977 persuaded him that his time at the top was up.

His height and reach constituted an enormous advantage at the weight and would surely have enabled him to dominate most other middleweight eras in much the same way.

Hopkins certainly still has time to surpass his fellow legends and achieve the all-time greatest immortality he craves.

He will go a great way towards doing so if he fulfils his ambition for three more successful defences including a crack at the light-heavyweight crown.

But for all his history-making bombast, for the time being at least the Philadelphian still has a way to go to emulate the greats of history.

Top five: 1 Carlos Monzon; 2 Marvin Hagler; 3 Sugar Ray Robinson; 4 Bernard Hopkins; 5 Harry Greb.