The problem with defining moments is that at the time you cannot be sure what the moment is defining. So you fail a job interview, but are pushed into your ultimate vocation as a consequence; or you leave a bride at the altar and end up with the wife of Beelzebub instead.
Such imponderables may race through Sergio Garcia's mind this week as he passes by a certain tree on his way down the 16th fairway of the Medinah Country Club. As he looks down at the roots he may think to himself: "Ah, that's where it all started." But then the penny should drop.
What exactly did start at that US PGA Championship of 1999, when a fearless teenager refused to let a 60ft immovable object block his dream and instead executed one of the most audacious strikes in golfing history? What was signified by the swerve of young Sergio that somehow found the green from the graveyard, and made Tiger Woods pull out stops he wasn't even sure were there?
Was this the gust of change from El Niño that we all thought it to be, or, in truth, was he - as some are now suggesting after yet another could-have-been at Hoylake - blown out by the age of 19? In fact, did not this moment define a career of glorious failure, rather than one of success?
Seven years on, back at Medinah, here is another US PGA and another major for Garcia to prove success is still possible, and so stride on to what he has always maintained is his destiny. Excuse the nostalgia junkies among us, however, for looking backwards, not forwards. The images of the last major of the last century simply demand to be replayed, as much as for what they now represent as for their magnificence in their own right.
There is Tiger with an unassailable lead, about to win his belated second major... but what's this? A skinny kid from Spain daring to challenge him and daring to steal the crowd's cheers with a six-iron gouge from the base of a trunk and a Boy's Own run and scissor-kick to witness his own magic? As Ben Crenshaw said so breathlessly on the telecast: "That's the future of golf right there." Except it wasn't. As ever, the future was about to manifest itself in a far less thrilling guise; over eight feet on the 17th green.
The significance of Woods's clutch putt for par was perfectly straightforward from a tournament standpoint, because if he had missed it his five-shot lead would suddenly have been nought. But what obviously could not have resounded so ominously was what this instant stood for. It told us that the reinstated world No 1 does not give up leads in majors. And the aftermath showed it.
Who knows if Tiger would still have embarked on his unprec-edented run - winning 18 of his next 36 starts and six out of his next 10 majors - if he had crumbled that day, although the world No 1 himself has since admitted what it meant to him. Two-and-a-half years had elapsed since he had chalked up major No 1 with such foreboding at the Masters, and all the whispers of false dawns must have been reverberating around his brain with such fury that a close-season of angst could have caused his psyche unshakeable damage.
Recent events have informed us, of course, that there is nothing Woods cannot get over, and that is what makes this return to the scene of what was arguably his most important triumph so pertinent. If it is a chance for Garcia to exorcise his demons at their birthplace, then for the overlord it is the opportunity to resurrect the God-like. Indeed, another era of omnipotence may already have begun.
Hoylake certainly appeared a watershed. The 30-year-old's Open is already the stuff of golfing folklore as he overcame the death of his father, Earl, to do it on his own, in his own way, with a display of such control, invention and, most of all, nerve, that he seemingly discovered a new plateau.
In contrast, Phil Mickelson has strangely fallen from his, so much so that it is incredible to think that it was only 73 major holes ago that he was on the 18th tee at Winged Foot, needing a par to become the third player in history to win three majors in succession. Where is that Phil now? The answer is: preparing as meticulously as he has been for the past three years, a fact backed up by his spending 13 hours at Medinah last Sunday and Monday. Mickelson discovered the longest major layout ever (7,561 yards) and a course where the driver is apparently compulsory.
The word "apparently" is used because Woods in winning his 50th PGA Tour event at the Buick Classic last Sunday hit his five-wood down the last hole some 302 yards with only normal run. This shot is called the "stinger", and it may give Mickelson the biggest rash of all. The defending champion has been landed with the draw from hell in partnering Woods for the first two days, and should he wish to stop his nemesis, then he will likely have to do so, head-to-head, over all four rounds.
Which isn't likely, especially when Steve Williams, Woods's caddie, is adamant that his employer is swinging the best he has seen since he first joined him. That was way back in 1999, in the run-up to, you guessed it, the US PGA at Medinah. Funny how things come around.