WIMBLEDON, England -- Confidence, as slippery as a wriggling eel, cannot be seen or touched or tasted. Still, you can smell it coming a mile away.
Like true love, confidence cannot be bought; it must be earned. It's about belief, a faith based on a history of success.
These days, does confidence genuinely reside in Roger Federer's heart and mind?
Here at the All England Club, where the world's tennis media have gathered in impressive numbers, this is the leading question.
After winning only four games from Rafael Nadal in the French Open final -- the worst Grand Slam loss of Federer's career -- many believe they see a worst-case scenario after studying his Paris Rorschach test. Every news conference is an opportunity to probe and to assess his frame of mind. But reading between the lines of his usually polite responses, all of this amateur psychology seems to irritate the world's No. 1 player.
"Why do they want to shoot me so soon?" Federer asked Neil Harman of the Times of London.
Federer is continually put in the position of defending himself. He does this by patiently reciting his results, and trophies are tangible evidence of that confidence.
"I haven't been reading and I haven't been listening to what has been said," Federer said after his first-round match. "So, of course, I haven't been affected, either. So I've been working in there as defending champion, opening Centre Court, trying to defend the title again. That's all that mattered to me.
"I came from a good tournament in Halle [Germany]," he said. "I couldn't do any better than not dropping a set, not dropping a service game, so I feel like I'm right there to do the same thing again this week."
So far, that's just about how it's working out. On Friday, Federer defeated Marc Gicquel 6-3, 6-3, 6-1 and now he'll have the weekend off.
Federer has won 37 straight matches at Wimbledon, 62 straight on grass and he's held serve in 89 of 91 service games this grass season. He's been the No. 1-ranked player for 230 consecutive weeks. These facts have not been lost with the bookmakers. Before the match, British bookmakers listed Federer as a 100-to-1 favorite, meaning you needed to invest 100 pounds to win one pound.
"He's extremely motivated," said Tony Godsick, Federer's long-time agent. "He loves it here. He won the junior title here, he beat Sampras for the first time here, won his first major here. The Olympics are here in 2012."
Federer said on Friday that Wimbledon is what's closest to his heart and he wished that someday his career might end here.
According to Godsick, the well-publicized bout with mononucleosis early in the season was an enormous factor in his slow start, which included a semifinal loss to Novak Djokovic at the Australian Open. When Djokovic, the young and rising Serb player, reached the semifinal at Roland Garros, it was the fifth straight time he had advanced to the final four of a major. He then later told the world that Federer was vulnerable.
"He was vulnerable at the beginning of the year," said Godsick, who, after Federer's girlfriend Mirka Vavrinec, is the supporter seen most often in the Swiss player's friends box. "He was sick. Luckily he didn't know it and played through it. It slowed him down. He didn't have enough practice time. And, with the Olympics, this is the worst year to get sick."
Djokovic is at Wimbledon here after a second-round loss and Federer looks to be on track for a record sixth straight final. So who is vulnerable -- and worried -- now?
Federer has reached 16 straight Grand Slam semifinals, an achievement that is difficult to fully process. This is far beyond the previous Open era record of 10 belonging to Ivan Lendl.
In the four years from 2004-2007, Federer won 11 of the 16 majors contested, a streak that John McEnroe calls "the four greatest years in the history of Open tennis."
"He's been to 16 straight Grand Slam semifinals?" said McEnroe, who is broadcasting here for the BBC and NBC. "How many of the top players have even played in 16 straight Grand Slams?"
"Yes, that's a good thing," Gilbert said. "It means he's got to keep it going, got to re-up, man."
Much has been made of the swift -- and difficult -- transition from clay to grass after the French Open, but how about Federer's transition from devastating loss to a flawless 8-0 on grass?
"He has always had a great ability to compartmentalize," Godsick said. "As good a winner as he is, he's a better loser."
"The key to coaching is short-term memory loss," Gilbert said. "The French -- that's gone, that's over. He gets tired of answering all the questions. He's thinking, 'Just look at the results at the end of the tournament.'
"He's got a quiet cockiness."
Whether it's Tom Brady with the ball during the fourth quarter of a Super Bowl, Mariano Rivera coming in to save the game in the ninth inning, Kevin Garnett rising in the paint to block a shot with the game on the line, or Federer in a Grand Slam final outside of Paris, demonstrated ability is a wonderful hammer to have in your tool chest. Federer is 12-for-12 in Grand Slam finals not held in Paris.
McEnroe used the words "superb" and "unbelievable" to describe the level of Federer's play on Friday.
"Going forward," McEnroe said, "this will give him more confidence, not that he needs it. It seems almost casual, that's how easy he makes it look. We saw a master at work."
Federer, sweat still oozing from his forehead and a little out of breath, did a brief interview with the BBC after beating Gicquel.
"Not losing a set against tough players, I like the way I'm playing," Federer said. "I'm looking forward to a few days off."
Federer was asked what areas of his game he'd like to improve.
"Well," said Federer, clearly perplexed by the question. "I just want to keep the game where it is."
Patrick McEnroe, the U.S. Davis Cup captain, has seen this phenomenon before.
"Is he supremely confident?" McEnroe said. "I think up until he plays Nadal, he is. And then he would be just confident. That might be enough.
"We really don't know. We'll find out. That's what we're all watching."
Greg Garber is a senior writer for ESPN.com.