Many people don't like being alone. They feel lonely. For others, though, it can be a source of ecstasy. The BBC's Shabnam Grewal spoke to a hermit on the Scottish moors, and learned about an American who turned his back on the world when barely out of his teens.
In 1986, 20-year-old Christopher Knight drove into a forest in rural Maine. He abandoned his car, and taking just some very basic camping supplies, simply walked into the woods. He didn't come out again for 27 years.
After getting deliberately lost, Knight eventually found the site that would become his home, a small clearing in the densely wooded area surrounding a lake called North Pond. He stretched some tarpaulin between trees, put up his small nylon tent, and settled down. He was completely hidden, despite being only a few minutes' walk from one of the hundreds of summer cabins that dotted the area.
Knight survived by breaking into these cabins and a community centre and stealing supplies. He only took what he needed - food, cooking fuel, clothes, boots, batteries for torches and a lot of books. He tried to cause as little damage as possible, but the sheer number of break-ins - more than 1,000 over the years, caused a lot of anxiety for some of the cabin owners. Eventually the police set a trap and caught him red-handed.
The writer Mike Finkel visited Knight in prison when writing his book, The Stranger in the Woods: The Extraordinary Story of the Last True Hermit. He asked him the obvious question, "Why?" Why had he turned his back on the world and gone off to live completely alone?
"Chris Knight said he felt very uncomfortable being around other people. Now I had thought at first that there might have been a specific triggering action. 'Did you commit a crime? Was there something you were embarrassed about? Was there a specific action?' And he insisted that there was nothing like that at all. He said the tug to be alone was like this gravitational force, all his body was saying that he just felt more comfortable by himself."
This tug was so strong that he chose to spend nearly three decades without speaking to a single person. Well, almost. He did speak to one person - he said "Hi" to a hiker who stumbled upon him one day.
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Despite the bitter Maine winters, when temperatures can plummet to -20C, Knight says he never lit a fire, in case the smoke attracted attention.
"There are many aspects of the story of Christopher Knight that boggle the mind," says Finkel.
"If you went one night in the woods of Maine in winter, camping in a thin-walled nylon tent, and didn't light a fire, I'd be pretty impressed. If you did it for a week I'd be amazed, and a month would be beyond belief. And this guy did it for 27 entire winters."
Knight told Finkel that he would instead go to sleep early, around 7pm, and set an alarm for 3am, the coldest time of the night. Then he would get up and walk around till morning, to stay warm.
Finkel then asked him what he did to occupy his time.
"For a little bit of the time he read some books, did the crossword... but really that did not occupy the majority of his time. What he did was what you and I might call 'nothing'."
If the idea of sitting alone, for half an hour, with nothing to do - think of being stuck, alone, in a lift, while your phone is sitting on your desk - is a little terrifying, then try imagining what it would be like confining yourself to a little clearing in the woods, for days, weeks, months, years…
"When I asked Chris Knight to explain this nothingness, he had some pretty interesting things to say," Finkel says.
"First he was never for a moment, in all 27 years, bored. He was never lonely. He said that he felt almost the opposite of that. He said he felt utterly and intricately connected to everything else in the world. It was difficult for him to tell where his body ended, and the woods began. He said he felt this utter communion with nature and with the outside world."
It sounds like a mystical experience, but one brought on not by psychedelic drugs, but by solitude.
Christopher Knight spent seven months in prison for his thefts, and has chosen not to speak to any journalist other than Mike Finkel. But I have lots more questions so I Google hermits and find one happy to chat.
Sara Maitland lives in solitude in Scotland in a simple and beautiful house she built herself. From her front door you can see for miles and miles, across empty windswept moorland. She is a Christian, but unlike official Christian hermits (which still exist) she isn't supervised by the local bishop.
She says many people think being a hermit is selfish.
"If I say I want to sail a small boat all the way around the world and it will take me two years, everyone says, 'Oh how exciting!' If I say I want to go and sit in my house and not talk to anyone for two years, they say 'Have you got mental health issues?' or 'Why are you so selfish?'"
She adds, sarcastically: "I joke that wanting to be solitary is bad, sad and mad. It's immoral because it's selfish. It's sad because it'll make you miserable and it's mad because you must be a nutcase."
So how does she answer the question why she does it? What does she get out of spending long periods of time all by herself and in silence? The answer, she says, is "ecstasy".
"Silence is a place in which I can find ecstasy. I only get it in silence and most people I know only get it in silence. It is just a fabulous feeling. You know, you're walking along and quite suddenly you just say, 'Yes!' It's an extraordinarily intense response. Totally joyful."
Although she doesn't think it's only available to the religious, for her, this ecstasy is a connection with God.
"I'm trying to position myself so the gift of mystical prayer is available to me, because actually the presence of God is a terrifically nice experience. I think it's heaven! Literally. I think that is what it will be like in heaven, that extraordinary sense of fulfilled intimacy - that feeling that one desires from sex, which is of both being completely yourself and completely with another person, is I think, what prayer does for me. It's a very particular form of intimate conversation with another, and it just so happens the other is God."
Maitland says you need to be alone for a certain amount of time before you start to get this feeling, but sometimes other things happen too when you are all alone.
In A Book Of Silence she writes about her experiences of solitude, and those of others. She lists the different, but very common experiences of people who spend long periods alone. They include losing your inhibitions, and becoming who you truly are when you're not being polite or trying to please others. This might mean picking your nose a lot, singing loudly or forgetting to get dressed.
Or something she calls "sensory intensification", which for Maitland included her sense of taste becoming very acute.
"Food just tasted fabulous. But it wasn't it tasted particularly fabulous in any mysterious sense it just tasted MORE. So porridge tasted of PORRIDGE. But it also affected things like how strongly you experience physical things, like baths. Baths were fabulous - they weren't just some warm water, they became a completely luxurious experience. When you got cold, you got incredibly incredibly cold, or incredibly wet and just FELT it."
And then she began to hear things.
In fact auditory hallucinations are a common experience for hermits, and she heard the sound of a huge choir, singing in Latin, coming from a small room in the small house she was living in.
Maitland enjoyed most of these and other effects of solitude, but only because she had chosen to be there. She thinks someone held against their will, in solitary confinement might, instead of a wonderful choir, hear nasty voices telling them to hurt themselves. Or their sensory intensification might mean the sound of a toilet flushing, becomes painfully loud and intense. In fact, one UN special rapporteur on torture called for solitary confinement to be banned.
But even in everyday life, being alone can feel really hard. Maitland notes that people often encounter silence for the first time after a loved-one dies, or when a relationship breaks down. She thinks it would be better if people learned in childhood to experience solitude as something positive.
"I say never ever use 'Go to your room on your own' as a punishment. You [can] use it as a reward. 'Darling you've been so good all day. You've been so helpful. Why don't you go to your room for half an hour now and be on your own.'"
For Christopher Knight, the hermit from Maine, the solitude and silence were the reward. He wanted to live out his life in that small place in the woods, to die there among the trees, leaving nothing behind.
"In this age of Facebook and social media, this is a person who literally wanted nothing known," says Mike Finkel. "He never had a camera. He never kept a journal. Nothing. He wanted to live completely unknown, and came close to succeeding."
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