Then, the unexpected intimation that Phelps may actually belong to a place different from the one the rest of us inhabit. What would he do if he didn’t swim? “I have no clue. I’d probably in the real world having a job.”

If it is in the real world that his worth is being assessed, his achievement is already two-fold. One, he has taught us new things about the human body. Oh no, it is not myth-building when they refer to his metabolism, says Susan Casey, a writer with Sports Illustrated. (No, the reference is not to his 12,000 calories-a-day diet.)

She writes: “For Phelps, with his 17 races, recovery is key. Exertion creates lactic acid, the athletic equivalent of kryptonite, and there are perfectly legal ways to minimise its residency in the body. Longer warm-downs, for one. Three minutes after Phelps’s race, or theoretically when lactic acid production is at its highest, someone will prick his ear with a needle and that blood will be measured to see how many millimoles of muscular waste must be cleared from his system. Phelps will then swim easily until the readings drop to an acceptable level.”

He wears the LZR Speedo suit, that’s credited with a flurry of new records. He has a body suited to the waters, wide armspan, for instance. To these he’s added his hard work — the money deposited in the bank.

Two, Phelps matters because he’s begun what only the greatest can, a historical reassessment of everything that’s come before him. So, this month when every hero’s pedestal is reassessed for size, when the worth of everything that has ever happened at an Olympic Games before is revisited, know that this has been made possible by the extraordinary achievement of a guy with a very goofy grin.