The 2008 TIME 100

When I was learning how to climb mountains as a blind person, I had a lot of encouragement from experts. But after I summited Mount Everest, these people weren't ready to accept what I had done at face value. Some said I must have cheated; one even claimed I had an unfair advantage: "I'd climb Mount Everest too if I couldn't see how far I had to fall."

Similarly, when Oscar Pistorius' lower legs were amputated at age 1, few would have banked on this South African challenging world-class sprinters. At 20, when he began to close in on an Olympic-qualifying time for the 400 m, experts posited that his times were so good, he must have been getting an un-fair advantage from his bladelike prosthetics. When he set his sights on the Olympic Games in Beijing, the International Association of Athletics Federations (IAAF) ruled he couldn't compete against able-bodied athletes. An IAAF-initiated study found that more energy is returned to Pistorius' upper legs from his blades than from ankles and calf muscles and that he uses less oxygen.

Pistorius, 21, is appealing, on the basis of studies with differing results. It was only recently that living with prosthetic legs was seen as a huge impediment, but he has turned this perception upside down. He's on the cusp of a paradigm shift in which disability becomes ability, disadvantage becomes advantage. Yet we mustn't lose sight of what makes an athlete great. It's too easy to credit Pistorius' success to technology. Through birth or circumstance, some are given certain gifts, but it's what one does with those gifts, the hours devoted to training, the desire to be the best, that is at the true heart of a champion.

Weihenmayer is the only blind person to conquer Mount Everest