Why climber Alex Honnold scales sheer rock faces hundreds of metres above the ground with no rope for protection — where the slightest misstep leads to certain death — is a question that has perplexed many around the world.
For the 33-year-old U.S. climber, the answer is pretty simple.
"Why does anyone do anything?" said Honnold.
"The most basic reason is because I enjoy it. I enjoy the movement of it."
Over the last decade or so, his free solo feats — climbing without a rope or harness — gained him fame within the climbing community.
Last year, that fame exploded internationally when he free solo climbed all 914 metres of El Capitan in Yosemite National Park.
The unprecedented feat — described by some as the climbing equivalent of walking on the moon in terms of sheer achievement — was captured in the sweaty-hand-inducing documentary Free Solo.
That film later won an Academy Award and BAFTA Film Award, bringing new attention to climbing.
But free solo climbing, while undeniably cinematic, is criticized by some for being too risky.
The adventure-focused nutrition bar, Clif Bar, which features a climber on its logo, dropped its sponsorship of a handful of athletes, including Honnold, in 2014 because of concerns about the risk of activities like free solo climbing.
"Some climbers feel these forms of climbing are pushing the sport to new frontiers," the company wrote in an open letter explaining the decision.
"But we no longer feel good about benefiting from the amount of risk certain athletes are taking in areas of the sport where there is no margin for error; where there is no safety net."
For Honnold, who has been climbing for decades, it's a personal risk he's willing to take.
"I'm afraid of dying, probably the same as anybody else," he said.
"But the appeal of free soloing is to take something that seems like it should be very scary and then feel confident to the point that it's no longer scary."
As Honnold pointed out, Free Solo focuses on the few hours he climbed unroped — not the two years he spent practicing the moves and meticulously preparing.
That's something that could be lost on new climbers though, according to Brandon Pullan, editor-in-chief of Canada's climbing magazine Gripped.
"Free soloing should be left to the people with a lot of experience in climbing," Pullan said.
"New climbers should not be free soloing because there is a lot of intricacies to climbing that a lot of new climbers don't totally understand like rock quality, how to downclimb [to climb down off the rock instead of being lowered with a rope], things like that."
Pushing the bar
But feats like Honnold's free solo climb of El Capitan push climbing, and what's possible, forward, he said.
"It was the most important climbing achievement," Pullan said. "It pushes the bar higher than it's ever been before."
Climbing without ropes is part of the history of climbing, he added, with many well-known climbers around the world pushing the limits to varying degrees.
"Free soloing goes back to the roots of climbing itself," he said.
"Most people who have been climbing long enough see it as part of climbing, something that climbers are going to do."
Ethical questions of witnesses
But free solo climbing also poses ethical questions about the responsibility people have to those around them who might witness a fall.
Honnold argues that individual choice trumps accountability to others.
"I know that it would be terrible for my friends to see me fall but, arguably, it would be worse for me — I'd be dead," he said.
"I've always considered my feelings on it to be more important than those around me. Obviously that sounds extremely selfish, but I've always felt like that is true."
For Honnold, it's about following passion — and that's what he hopes people take away from what he does.
"I talked to more people who signed up for a marathon after watching the movie than people who want to go free solo," he said.
"There's so many things in life that you can think about forever but, at some point, you actually have to do the work."