It's a bit like asking, how does an aircraft stay up? So long as it does, who cares?
The enigma that is Georgios Samaras has divided supporters since the day in January 2008 the Greek international walked in the front door at Parkhead.
His arrival as a loan signing was immediately questioned, given that his two-year tenure at Manchester City following a £6million transfer from Dutch club Heerenveen had been an unmitigated disaster.
The escape to the SPL was predicted to provide short-term respite for the troubled youngster.
However, as he approaches his fifth anniversary as a Celt, Samaras now stands as a man who has not only won games, but the respect of the support.
Sure, the 27 will still frustrate when he misplaces a pass, or mishits a shot, his long hair framing a face which frequently carries an expression of complete disbelief that something he has attempted has not come off.
But when he is not in the team – which now tends only to be because of injury rather than non-selection – the value of Sami is clear for all to see, even those who were his biggest critics.
The important goals scored in crucial games – as in Moscow last week and against Hearts at the weekend – merely underline why Gordon Strachan brought him to Glasgow, and why Neil Lennon was prepared to stick by him.
If Lennon is the leader of the fan club, then new recruits are being added every week, and every goal swells the membership.
But is it a case of Sami seeing the light, or the supporters becoming switched on to him?
One man who has always been in the big man's corner is Bobby Lennox.
Known to score the odd goal or two on the European stage for the Hoops in his time – 273 times he hit the net in 571 appearances to rank as the club's third-top scorer of all time – Lemon revealed he has been enthused by Samaras from the very start, because his honesty shone like a beacon.
"I've always liked him," said the man who terrorised defences with his pace and power coming from the left side of Celtic's attack through a two-part Hoops career which stretched from 1961 to 1981.
"Sami works his socks off, has great ability and carries the ball very far up the pitch, which is a great asset for any team to have.
"He doesn't always make the right decisions. But then, tell me a player who does?
"What he does do is play his part in helping the team, and he is good in both boxes.
"His ability in the air is very important to this team, though his team-mates do not always get close enough to make the most of his flick-ons."
Lennox would back the big man to win most of those headers, but he can become as exasperated as anyone else watching Samaras when he gets it wrong.
"Sure, he can infuriate at times," said the sprightly 69-year-old who now spends as much time on the golf course as he does watching football.
"But you can never say he doesn't give his all. And he is always looking to be positive, which is why he can light up games."
When he glides past a defender, the crowd rises in unison. But they can also sink to their seats as one if the move does not quite go according to plan.
Samaras' expression can betray how disappointed he is, but Lennox refutes any suggestion he has a lackadaisical attitude.
"Sami can look unconcerned at times, but he is not," said the Celtic legend. "He does want to do his best all of the time, though that's not always possible.
"Considering his ability, I don't think he scores as many goals as he should.
"But he is on a decent run, and his goals, when they do come, tend to be important ones."
Samaras can point to the fact he has scored in all four of Celtic's away wins in Europe in his time at the club – Moscow twice, Helsinki and Helsingborg.
Lennox knows from his own vast experience how tough it is to find the net on foreign soil, and applauds Sami's record.
However, he added: "Listen, scoring goals anywhere is the ultimate test of an attacking player.
"And the key to this is the same as it has always been – confidence.
"If a player is confident, he believes he can do anything. If not, he's just as likely to fall over the ball."
That's an area in which Lennon and his backroom staff have invested great time and energy to ensure Samaras takes to the field feeling good about himself.
The manager also placed a lot of his own reputation on the Greek international's shoulders, famously admitting at a club AGM that he is the kind of player who can get a manager the sack.
Lennox reckons Lennon knew it was never that much of a gamble, and explained: "Neil praises him, and let's face it, he is in the best position of all because he sees him every day in training."
Now Samaras faces his toughest test to date when he must deliver for his manager and the won-over support in the Nou Camp against Barcelona.
The mention of this Champions League game lifts the excitement level in Lennox's voice.
He has played on some of the biggest stages football has to offer, and is tipping Sami to rise to the challenge and the occasion.
He said: "Playing in Barcelona will not faze him. These are great games to play in. And, the way things stand, if Celtic lose, oh well. But, if they can take something, they will be heroes.
"They already have four points from their opening two games in the group, which is a good start.
"As a team we always thought we had a chance, wherever we played, and I can see that belief starting to grow in this group.
"It was certainly there in the closing minutes of the game in Moscow where they had the confidence to really go for it.
"It was a great header from Sami for the winner, but they deserved it."