Nobody knows anything.

William Goldman’s caustic observation on Hollywood applies equally to the winning of titles. If there was a formula to enlisting players who were capable of winning leagues, then everyone would be applying it. If there was a precise path for a manager to follow to a championship, then all would be following the map.

This does not stop everyone, of course, coming out with observations that suggest there are unarguable constants. The most famous is Alan Hansen’s comment about the talented Manchester United side of the 1995-96 season: “You win nothing with kids.” Unfortunately for Mr Hansen, no stranger to winning titles, that generation of kids proved to be the most relentless achievers in the modern English game.

The theory, too, that it is all about “bottle” is fatally flawed. The Celtic side that surrendered the title at Fir Park in 2005 was a side heavily marked by proven winners. The line-up that day was Rab Douglas, Didier Agathe, Bobo Balde, Stan Varga, Jackie McNamara, Stiliyan Petrov, Neil Lennon, Chris Sutton, Alan Thompson, John Hartson and Craig Bellamy. Valid accusations may be made against this side but a lack of conviction is surely not among them. They were also experienced winners, but they came up short.

Similarly, the Rangers side of this season has been routinely described as a team that grinds out results, will not back down and always prevails in a tight race. Yet it contains in the squad five members of the team that came up short in 2008 with a 2-0 loss to Aberdeen, in Neil Alexander, David Weir, Steven Whittaker, Steven Davis and John Fleck.

Both the 2005 Celtic team and the 2008 Rangers side succumbed to the tyranny of other factors. The chief amongst them was fatigue. Martin O’Neill’s Celtic side was running out of legs and Walter Smith’s Rangers side had endured a hard season in Europe, culminating in a defeat in the UEFA Cup final.

It is accepted that tiredness, loss of form and injury can lead to the concession of a league title. So far, so obvious. But what wins it?

As Celtic and Rangers face a combined total of nine matches to complete the season, the search for the X factor has begun with the usual suspects being paraded. Experience, form, squad and the potential difficulty of the respective fixture list are the obvious points of interest.

Experience is key but -- witness 2005 and 2008 -- it is not a guaranteed title-achiever. In terms of experience, too, Celtic are hardly brash youngsters. As the panel shows they have a glut of players who have won championships, four of them with the club. Others have taken titles in England, Ireland, Scandinavia and Central America.

The form of both sides is also now good. Since limping away a beaten side from Tynecastle in November, Celtic have played 28 matches, only falling to Motherwell in the league and to Rangers in the final of the Co-operative Insurance Cup.

Rangers have come through a difficult month. Defeat to Dundee United at home was followed by narrow victories against St Johnstone, Hamilton Academical, Aberdeen and St Mirren. Smith admitted his side was looking “flat” in that period but the rout at Tannadice and the performance in Sunday’s Old Firm match show Rangers have found a vigour that means the race is not yet over.

The squad argument is now slowly losing its importance. Rangers have only four matches to play. They lack the resources to “freshen” the team but may not need to bring in anyone as Smith is certain to play the hand he has been dealt. His only worry would be any injury to Nikica Jelavic, who has been central to Rangers’ ability to prevail in recent matches.

Celtic have both the numbers and the quality to cover in all positions. The absence of Joe Ledley, who underwent a scan on a hamstring strain last night, will be a blow but not necessarily one that will dismiss title hopes. Lennon has options in midfield that include Ki Sung-Yueng or Scott Brown partnering Biram Kayal in the central area. Freddie Ljungberg can also be thrown into the mix with James Forrest, Kris Commons, Niall McGinn and Paddy McCourt options on the wings.

The difficulty of the respective fixtures is, frankly, difficult to assess. Rangers would appear to have the easier task with Motherwell (away), Hearts (home), Dundee United (home), Kilmarnock (away). Celtic have one more game with Dundee United (home), Inverness Caledonian Thistle (away), Kilmarnock (away), Hearts (away), and Motherwell (home).

There was a mass of media opinion that suggested after the Old Firm match that both teams would win their remaining matches. This nine-match accumulator is far from a certainty.

This lack of precision is the crux of the matter. Sir Alex Ferguson, the Manchester United manager, who has won a few titles over the years, is a firm believer in the power of luck. Walter Smith, when asked what he most wanted to bequeath to his successor, Ally McCoist, replied: “Luck.”

This good fortune can be crucial when the teams are locked at the top of the league. The factors of experience, form and all else can be argued and assessed but how can one factor in football’s facility for introducing the highly unlikely.

In 1995, Manchester United had to beat West Ham United to win the championship. Andy Cole, who scored just about a goal every two games for United, was through on goal so often he could have used the afternoon to double his career tally. He did not score once. In 2005, Scott McDonald scored twice in three minutes for Motherwell to dump Celtic.

The cliche is that it is not over until the fat lady sings. The smile of Lady Fortune can decide who joins in that chorus of celebration.