The intensity of a final-day battle at The Open Championship can produce pressure so ferocious it forges greatness.
Last year's spectacular Sunday showdown between Henrik Stenson and Phil Mickelson did just that.
But that same incalculable force can also make men wilt, as Jordan Spieth appeared very much to be doing at Royal Birkdale's 13th hole.
There were times when Spieth's round was hard to watch, and others when it was harder still to believe.
What an incredible way to comeback and win. Many congrats @JordanSpieth-- Tiger Woods (@TigerWoods) July 23, 2017
The three-stroke lead on which he slept was gone by the fourth hole and it's not like Matt Kuchar had hunted him down.
Spieth bogeyed the first, third and fourth. He was melting.
Walking off the ninth - which Kuchar birdied as Spieth dropped another shot - they were level again and that parity remained until the 13th.
What transpired there was decisive, but not in the way anyone could have predicted.
Spieth sprayed his tee shot wildly to the right and put his hands to his head, open-mouthed as his ball disappeared behind a grassy mound.
The 20-minute spell of confusion and bemusement that followed offered time enough for most onlookers to surmise that the psychological fragility so evident in Spieth's 2016 Masters collapse had returned to haunt him in Southport.
He took a drop on the practice ground, which seemed apposite.
But it was then - when the heat was at its most searing - that Spieth stood tall, held firm and forged his own legend at golf's most storied major.
It may have started with a scrambled bogey five, which saw the 23-year-old lose his lead, but from there he ascended to another level.
Spieth very nearly aced the 14th, settling for a short birdie putt to level it up, then snaffled up a long eagle opportunity, following that with another two birdies.
In just four holes, the Texan had turned farce into fantasy, failure into formidable triumph.
So when he closed with a par at the last, he signed not for a stunning 63 like Stenson had at Royal Troon, but a relatively modest 69.
And yet there was something just as remarkable about Spieth's round as there was the Swede's, if not more so.
While Stenson was sublime throughout, the 2017 Champion Golfer of the Year had to rediscover his best self two-thirds of the way through one of the most important rounds of his life.
That requires precisely the kind of mental fortitude that Spieth had been so readily accused of lacking.
He already had two majors to his name, but this one seems somehow to define him more than any triumph that has gone before.
In an era when golf's four biggest titles are shared around so freely - Spieth's success halted a run of seven consecutive first-time major winners - a player with one or two is not all that rare.
A man with three, who can complete a career Grand Slam at next month's US PGA Championship, is an altogether different beast.
Spieth will be 24 by the time of that tournament at Quail Hollow and victory would ensure he completes the clean sweep six months earlier than Tiger Woods managed.
His route to the Claret Jug this week may have involved a few exasperating diversions, but the path to golfing immortality is now clear for this exceptional talent.
Jordan Spieth, once a legend in the making, is now a legend made.