The debate is not academic. Many athletes have not made it to the Games upon being detected for doping. Samples are now being frozen, so that once new diagnostic methods are found, they can be checked for substance abuse again. This summer the US relay team (4x400m) had its gold medal from Sydney 2000 taken away and awarded to Nigeria, upon one of the runner’s confession on doping.

In fact, take the example of the 100m, the Olympics’ most visceral race, which has been hit hard by doping. Ever since Ben Johnson ran past Carl Lewis in Seoul 1988, recording 9.79 seconds, only to be found out for steroid use, suspicion has always attached to champions. American Justin Gatlin, who won the 100 m at Athens 2004 in 9.85 seconds, subsequently began serving a four-year ban upon a positive steroid test. In 2007, Marion Jones had her gold medal from Sydney 2000 taken away after she confessed to steroid use during that period.

This is perhaps why Phelps is so valuable to sport today. It’s not about the number of medals he may finally take away from Beijing. It’s not about the records he may yet break here and elsewhere. It is that when he does something, he reinforces our belief in pure human excellence.