It is incredibly difficult to think about nothing but your most basic needs.
Try it, now. Go on. Stop thinking about other people, your job, your list of responsibilities. Go into an animal state. Focus only on hunger, thirst, and the sensations of your body. Truly take in your surroundings, without being half-elsewhere, consumed with planning and worry. Actually be in the world. How did you go?
When you're on a long-distance hike, it's the only way you're able to think.
Simon Morris lost 15 kilograms and wore through three pairs of shoes on his four-month hike from Springer Mountain, Georgia, to Mount Katahdin, Maine: the 3,500 kilometres that make up the United States' Appalachian Trail.
Like all hikers, he spent the majority of that time in the drugged-like state that comes from exhaustion, exposure to the elements, and severe calorie-depletion.
It's a highly-concentrated existence where the whole world collapses into the question of whether or not you have the willpower to take one more step.
Which would be the whole point.
"It's a whole different way of life," Mr Morris said.
"It's a very simple way of life. A lot of people find it very significant; it leaves a very significant impression on your life. You're concerned with water, how much food you've got, how far you're going to travel that day.
"Once you've been going for a while, people will say to you, 'What's your birth name?' And you don't have a clue. You've got to think about it. But if they say, 'What mile are you at?' You can answer like" - he snapped his fingers - "that."
"How much food have you got?" Snap. "How much weight are you carrying?" Snap. "Where's the next water?" Snap. "You know all of that. But what's happening in the world? Have you heard what's happening in Russia? You haven't got a clue."
There is just your body, and the trail.
The Appalachian Trail is one of three trails traversing the US that make up the Triple Crown of hiking. There is also the Pacific Crest Trail, from the bottom of California to the top of Washington state made famous by the book Wild, and the Continental Divide, bisecting the country from New Mexico to Montana. Combined, they consist of 12,700 kilometres distributed throughout 22 states, and have been conquered by about 400 people over the past 25 years.
Mr Morris, 64, would very much like to conquer them.
Only about one in four people who attempt even one of the thru-hikes completes them, but Mr Morris is already almost there.
A retired nurse who spent more than 30 years at the Launceston General Hospital, Mr Morris first took a crack at the Pacific Crest Trail in 2015 alongside his wife, Maggie.
They made it more than halfway before deciding that Mrs Morris had lost too much weight to safely continue, and made the hard choice to stop and return to Australia.
Four years later, Mr Morris has just gotten back from a second trip. He completed not only the final section of the PCT, but also the entirety of the Appalachian Trail.
Next year, he'll set his sights on the Continental.
"I've probably seen more of America - a hiker would see more of America - than the average American," he said.
"You meet total strangers who, for no reason at all, will take you into their house, let you wash your clothes, feed you, and take you back to the trail. No problem at all. They don't want anything in return. They're just happy to see people living their life."
The Appalachian Trail takes its hikers through some of the less-touristed parts of America. It runs through isolated communities along the Appalachian mountains: towns where there is still no mobile phone reception, and where hikers would 'rejoice' if they found a restaurant with wifi.
In fact, the place Mr Morris commonly found mobile reception was on mountaintops. He describes calling his wife while crouched behind a rock, shivering through an active snowstorm, while grabbing the rare opportunity provided by a few bars of service.
Appalachia is Trump country, and Mr Morris said he had a preconceived image of what the people in those reclusive-seeming communities would be like. But, in fact, his experience of the region was one of welcome. It was defined by 'trail angels': people who leave boxes of treats for the hikers to stumble upon, or stand at trailheads barbecuing up a sizzling snack for the walkers at no cost.
There was also the camaraderie with the other hikers to keep him going.
On the trail, nobody uses their real name. It's a 'leveller', Mr Morris said, one that further reinforces the sense of a parallel universe that is a multi-month hike.
"You've got all sorts of people, from the unemployed to professors," he said.
"It doesn't matter who you are: there's a hill there, and you've got to climb it. There's no easy way out. You've got to put one foot in front of the other."
On trail, Mr Morris is known as Wow, short for Words of Wisdom.
The bombastic name is tongue-in-cheek. It was first bestowed on him on another hike, this one Tasmanian. In 2008 Mr Morris and a group of adventurers retraced the steps of 'cannibal convict' Alexander Pearce, bush-bashing their way from Strahan to Ouse.
Mr Morris was the one with the video camera.
"I'd go first and I'd film them struggling to get up somewhere, and I'd say 'have you got any words of wisdom?'" he said. "When we finished they made me a plaque with Words of Wisdom written on it."
After a long hike is over, the highlights and lowlights are indistinguishable. Everything gets muddled up in the mix of adrenaline and monotony - the hallmarks of any long-term adventure. Maybe it would be more accurate to put the stand-out experiences into one category: memorable.
There's arriving in a town and scoffing whatever high-calorie food you can get your hands on: Mr Morris recalls watching younger hikers buying whole sticks of butter and stirring it into peanut butter before spooning a whole jar of the disgusting concoction into their mouths.
There's the animals: beaver, moose and deer, a myriad of bird species - but also bears, and the accompanying friend-of-a-friend or online stories of attacks.
There's the trail itself, sometimes a simple walk in the woods - the Appalachian Trail is known as the 'green tunnel' - but sometimes involving rock-climbing up a pouring river, navigating an ice rink, or squelching through a bog.
It won't be too long before Mr Morris is hitting the trail again, with a plan to tackle the 5000-kilometre Continental Divide next year to claim his Triple Crown.
For those who most look forward to a comfortable armchair at the end of the day, it must seem an inexplicable undertaking.
"People always ask why," he said.
"Why do you want to walk for thousands of kilometres. And the answer doesn't come in words. The answer comes in the direct experience of actually being out there. It's on a daily basis. This is why.
"You run out of superlatives. You run out of words. It's just a matter of being there and going ... yeah. Yeah. This is why I'm doing it. It's a feeling. You just go ... yeah."
- Follow Simon Morris' Continental Divide journey from mid-April 2020 at the Monarch and Wow page on trailjournal.com
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