"Who is the greatest Olympian?" is a topic that sports fans have debated for decades, and they will continue to do so for as long as the Games are contested.
Most of the time when this argument is picked and pulled apart, it is the names of the most decorated athletes who come up with regular frequency.
I asked this question to a friend recently and the answer was predictably swift. "Phelps".
The American swimmer is an obvious choice. His 23 gold medals, three silvers and two bronzes make him by far the most decorated athlete in Olympic history.
Larisa Latynina, in second place on the all-time list, has a paltry nine gold medals by comparison.
When you add the Soviet gymnast's five silvers and four bronzes, she still comes up 10 medals shy of Phelps' tally.
Michael Phelps is a freak of nature, a superman athlete whose records, you would think, will not be eclipsed for a very, very long time. If ever.
But should we always plump for the most decorated athletes when deciding who is the best of the best?
It is unquestionably a remarkable achievement to win 23 Olympic gold medals, but having so many opportunities gives you a significant mental edge.
Training for the Olympics involves a gargantuan effort of blood, sweat and tears over a gruelling four-year period.
Knowing that all of your eggs will not be in the same basket when you get to the Games is clearly an advantage which athletes who compete in multiple events have over those who get just one shot.
Phelps competed in eight events when he won his first Olympic titles in Athens in 2004. If he messed up in one race another opportunity was just around the corner.
It must make it easier when you know you will have numerous chances for glory at the same Olympics. Any failure is almost like losing a life on a video game. A blow, yes, but it's not game over.
When the greatest Olympian debates begin to rage, a name that will likely not come up much, at least outside of Japan, is four-time Olympic champion Kaori Icho.
The wrestler struck gold at the Athens 2004, Beijing 2008, London 2012 and Rio 2016 Games, with her first three triumphs coming at 63 kilograms and the latter at 58kg.
On each occasion she had one chance for glory on the Olympic stage, and one chance only.
Icho, the first woman to win four consecutive Olympic gold medals in an individual event, did not have the luxury of a second-chance saloon. There was no wrestling team event offering another chance at gold, and no tournament with slightly different rules providing an alternative route to the podium.
"To say that Icho did not get the credit she deserved would be an understatement," said Ken Marantz, who is based in Tokyo and writes for United World Wrestling (UWW).
My argument is we should not always think of swimming and other Olympic sports with several events, such as athletics, gymnastics and cycling, when it comes to debating who is the greatest of all time.
Yes, competing in multiple events can perhaps provide its own pressures. If Phelps, for instance, had left an Olympic Village with just two golds from a single Games then it would have been regarded as a failure.
But this, I would suggest, pales in comparison to the pressures faced by athletes like Icho who know they have one, and only one, chance to perform to the best of their ability on the grandest of all sporting stages.
The Japanese wrestler is, by my reckoning, the only Olympic athlete to have won four gold medals in an individual discipline where she had absolutely no margin for error at all, and no consolation prize of another event to compete in.
Other Olympians have won four titles when competing in their only event at the Games, of course.
Everybody has heard of Phelps but who outside of sporting circles knows much about his American compatriot Al Oerter, a four-time Olympic champion in discus?
He won gold at four consecutive Games from 1956 onwards and it was of course his only event.
My British mind is also instantly drawn to sailor Sir Ben Ainslie, a four-time Olympic champion with three titles in the finn class and one in the laser, between 2000 and 2012.
Denmark's Paul Elvstrøm also won four golds on the water. He claimed the firefly title at London 1948 before a hat-trick of golds in the finn.
However, if you are being ultra, ultra pernickety about the achievements of Oerter, Ainslie and Elvstrøm, Icho still stands above them.
In discus, you don't just get one throw and that is your lot. Oerter knew that if he messed up with one attempt, he would be back. A miniscule psychological advantage, perhaps, but an advantage all the same. In his Olympic finals he threw six times.
Sailing events, meanwhile, take place over a number of days and crown winners after several races. A bad day on the water is not necessarily game over, and the sport's system of discarding a competitor’s poorest result means there is an insurance policy if things don't go well.
Ainslie, for example, was disqualified from his second race in Athens but it did not count to his score. He benefited from the tiniest room for error, and then took full advantage.
Icho had no luxury like this. In wrestling, bouts can be over in the blink of an eye. One wrong move, or one small lapse in concentration, can see you flipped onto your back and knocked out of the competition.
You cannot remove a poor bout from the scorebook or simply have another go. There is no repechage to get into the gold-medal contest another way.
Ultra-harsh critics will point out that when Icho competed at her first Olympics in 2004, the tournament began with a pool stage.
If all three wrestlers in a pool beat each other, it was possible to advance after losing a match.
Icho, of course, won both of her contests but the United States' eventual silver medallist Sara McMann progressed despite a defeat to Canada's Viola Yanik.
This system does not really offer a safety net because losing a bout means relying on a favourable result in the contest you are not involved in. You cannot afford to take your foot off the gas as that would mean taking your fate out of your hands, and only one wrestler went through from each pool.
At Beijing 2008 and London 2012, a best-of-three rounds system was in place. Each round lasted for two minutes, and if you were out-fought after one 120 second segment you could still go through if you won the other two.
Again, this perhaps means that Icho had the luxury of a slight insurance policy, but then again not really. Despite the rounds system, each contest was still a single fight and in a combat sport your opponent can neutralise you in seconds.
Icho, then, is in a league of her own. And it is not surprising that she triumphed on all four occasions when you assess the skill and style this phenomenal athlete possesses.
"It's hard to put your finger on everything she does well," said Tim Foley, the senior manager of media operations at UWW.
"She reduces risk. She minimises her risk more than anyone else.
"She's constantly manipulating time and space in her brain and coming up with the techniques necessary to score the points she needs to win.
"It's incredible the way she analyses opportunity and analyses risk.
"In wrestling, a lot of the time you are taught to 'go go go' and she does do that, but she's incredibly talented at managing a match and managing her opponent to ensure she's putting herself in the best position possible when time's running out."
Icho was born on June 13 in 1984 and trained at the same club in Nagoya for much of her life.
As the pressure on her grew leading into the Beijing 2008 Olympics, she contemplated retirement.
History knows this was not the path she took, but Icho was aware of the need for change after spending so much time with the same training partners and coach.
She made the bold decision to leave Japan and head to Canada, where she learnt different methods and her development into one of the greatest wrestlers of all time continued.
"I wanted to experience life overseas and see how foreigners trained," she said to UWW in a 2014 article. "The biggest difference that I saw was how well the athletes and coaches communicated."
On her return to Japan, Icho spent time training with the country's male wrestlers.
"Men are more profound in their detail and the moves are more complicated and that makes learning them a serious process," she said.
As well as her Olympic golds, Icho's glittering career included 10 world titles - the last of which came in Las Vegas in 2015.
It is clear that she developed the perfect formula to win matches over and over again.
"It was a mixture of strength, technique and just raw determination not to give up the points," said Marantz.
"As technically perfect and deceptively quick as she was, I think it was her defence that put her up and kept her on top.
"Every champion wrestler has great natural ability, quickness, great techniques and usually works harder than everybody else. Icho was no different.
"What I thought set her apart from her opponents was just how hard she was to score points on. If an opponent shot in and grabbed a leg, the battle was just beginning.
"People might see that and think, 'oh, she's in trouble now'. But it was far from a done deal. In the London Olympic final, the Chinese opponent got Icho's leg in the air, but still couldn't finish off the move. In fact, it was Icho who ended up getting the points."
It is important to note, too, that Icho is a product of the highly-competitive Japanese system.
Just reaching the Olympic Games was a huge challenge with no room for error, as her national opponents vying for the same quota places were among the very best on the planet.
"Japan's the most competitive nation for women's wrestling in the world," said Foley. "Some upstart could take her out.
"Never mind the fact that she was wrestling up a weight. There wasn't a lot of weight opportunities for her first three Olympics. She put on fat and muscle as well as she could and she wrestled up. She was out-strengthed all those times.
"She had to be creative, she had to manage her opportunities. Because she was wrestling so much above her weight."
In such a wrestling-mad country, you would think Icho would be a huge star. She has often played second fiddle to another Japanese legend, however, in the shape of Saori Yoshida.
Yoshida has won 13 world titles but her three Olympic golds leave her one short of Icho. She is another phenomenal athlete but could not match her compatriot as she attempted four in a row at Rio 2016, losing to Helen Maroulis of the US in the 53kg final.
When the Olympic Flame for the now-delayed Tokyo 2020 Games was ignited in March, Yoshida was one of the athletes given the honour of travelling to Greece to collect it.
Icho does not court the limelight but perhaps struggles for credit, even in her own country.
"She doesn't care much for publicity," said Foley. "She's always been very solitary. That's not to say she's not a good team mate, she is, that's not to say she's not a good friend, she is, she's just very conscious of what she needs to be better and she doesn't think that being on television which is a huge draw in Japan is part of that.
"Yoshida is widely popular in the country and was always more willing. Yoshida has always played the game while Icho was more interested in results."
Marantz admits that Icho being overshadowed by Yoshida has always "baffled" him.
Even Yoshida’s greater tally of world titles can perhaps be explained by Icho’s decision to skip the two World Championships after Beijing 2008 and the one following London 2012.
"To be fair, Yoshida seemed to actively seek the spotlight, while Icho pretty much shunned it," Marantz said. "They had different personalities, and I suppose it is no surprise that the media was naturally attracted to the one who was more outgoing.
"I am sure many Japanese were hoping that Yoshida would be the first four-time gold medallist. But because Icho did it, it finally gave her the national recognition she deserved."
In 2016, before her historic victory in Rio, Icho lost an incredible 13-year unbeaten streak when she was defeated by Pürevdorjiin Orkhon of Mongolia at the Golden Grand Prix Ivan Yarygin in Krasnoyarsk, Russia.
She was able to regroup and make history, seeing off Russian Valeria Koblova in the Olympic final in Brazil.
At the Sydney 2000 Games, many thought Russia's Aleksandr Karelin would win a fourth Olympic title in a row but the Greco-Roman great was beaten in the final. Yoshida missed out in similar circumstances in Rio, but Icho got over the line by dramatically spinning Koblova away for a takedown with just seconds remaining.
"In 2016 she actually lost earlier in the year," said Foley. "It's incredible to think that happened in the same year she won the Olympics.
"You would think that would have showed an acceleration downward or she's going to be upset by the whole process.
"She used it as an opportunity and she learnt a lot from that experience. In some ways that one loss might have been the thing that saved her in the end. Because she was able to correct and find solutions.
"You learn more from a loss than you do from a win."
"When an athlete wins as much as someone like Icho, it's hard to distinguish between the victories,” Marantz adds. "She's always made them look so effortless, which of course was not the case.
"The one match that sticks out is the final at the Rio Olympics. Not just because it gave her an historic fourth gold medal, but because it was the only time up to that point that I had ever seen her trailing so late in a match.
"I'm not even sure that in matches I personally watched that I ever saw her trailing at all. But the way she managed to break Koblova's hold on her leg and get behind in the final seconds just added to her legend as the best of all time."
In December 2019, Icho ended her bid for an unprecedented fifth Olympic gold at Tokyo 2020.
She hoped to qualify in the 57kg class but missed out on Japan's spot to Risako Kawai, a fellow Olympic champion.
If she had made it a magical five, it would have been unprecedented in men's and women's sport. Would she have finally got the credit she deserved? The jury is out.