In 1923, the mountaineer George Mallory gave an interview to The New York Times in which he famously explained why he was determined to summit Mount Everest. “Because it’s there.” He died in the attempt the following year. Alex Honnold, who last year became the first person to climb Yosemite’s El Capitan alone and without a rope, seems to have a different explanation for why he climbs. “Because I’m here.” ~snip~ But the thrills of the movie turn out to be incidental to its real purpose, which is less about climbing than it is about living. Honnold, it turns out,...