For Greta Garbo, solitude was a mantra; for Henry David Thoreau, an ideal; for Howard Hughes, an obsession.
But for more and more Americans today, it's just reality.
"I would argue that the rise of living alone represents the greatest social change of the last 60 years that we have failed to name or identify," said NYU sociologist Eric Klinenberg. "This is a transformation that has touched all of us, whether we live alone or it's just someone in our family or friendship circle who does."
Klinenberg has spent years tracking the seismic spike in "solo dwelling." He says today there are about 32.7 million Americans living alone. Clearly, if you live alone, you're NOT alone.
"It's an incredible number, and it's a massive increase over where we were in 1950 when it was just four million Americans," Klinenberg said.
One is no longer the loneliest number. Roughly four out of ten households are single-person homes, in cities like Seattle (42 percent), San Francisco (39.7 percent), Denver (40.4 percent), and Cleveland (39.9 percent).
And then there's Manhattan, an urban island where almost HALF of all households are made up of just one person - where millions of people seek safe harbor tonight in an empty apartment.
Does that sound lonely to YOU? Well, don't tell THEM that.
Bolick could be the poster child for the new American family . . . a family of one. Not even a cat to feed. "And you're not lonely?" asked Spencer.
Now 39, Bolick turned solitude into celebrity. Her 2011 article on living alone was one of the most widely-read pieces in The Atlantic's history. It netted her a major book deal, and even was optioned for a TV series.
"I grew up very close with my family, and I'd always had long-term boyfriends, roommates," Bolick said. "I thought, 'God, you know, who am I on my own when I'm not being supported by these people who love me?'"
"You almost make this sound like it was a test," said Spencer.
"Oh, that's a good way of putting it," she laughed. "I think it kind of was."
She aced that test. And sociologist Klinenberg says she should be proud. He calls single people "indispensible."
"They go out into the world like no one else does and spend time and money in bars and restaurants, in cafes, in gyms, in clubs," he said. "They're the ones who are most likely to go to public events - book readings, art classes, all kinds of public activities that give life to city streets."
So who are these wonderful people? Well, one-third (34.5 percent) are 65 or over, and about half (48.3 percent) are between 35 and 64.
And the women (17.2 million) outnumber the men (13.9 million).
"Women do a much better job when they're living alone," said Klinenberg. "They tend to make and maintain relationships much better than men throughout the life course, whereas for men it's much more likely that they will wind up feeling lonely or unhappy or isolated."
Case in point: Forty-year-old New Yorker Jeff Ragsdale. He describes waking up alone as "hell."
"It's very sad," he told Spencer. "Or going to bed, you know, alone constantly by yourself, eating alone. And also there's nothing worse than being sick by yourself. You're lying in bed watching the world go by and wondering, 'How did I get so alone?'"
Ragsdale didn't seek solitude; his girlfriend broke up with him. Desperate for human contact, he did the only logical thing: He posted flyers all over Manhattan inviting people to call. He signed them: "Jeff, One Lonely Guy."
"My guard was down, I was completely stripped. I'm basically posting this flyer that says I'm a loser, you know?" he laughed. "It wasn't a fun thing to put those up. But I needed to talk to people. So I go, 'I'm just going to rip my skin off, and I'm going to do it and let the cards fall.'"
Ragsdale expected a handful of calls. What he got was a full time job - and enough material for a book. He said he's had close to 70,000 responses by now - and six months later, he's still manning the phone.
"People from all over the world, well-wishers, and then I also became, like, a confession booth for some of these people - a marriage, relationship counselor, sex counselor, school counselor."
The response has convinced Ragsdale that, despite the trends, living alone is not a natural state of affairs. He says people who claim they can thrive on solitude and the freedom it suggests are "a very small percentage of people. And those people I would suggest are wired differently, 'cause it's completely against our instincts."
So the debate rages. Was John Donne right or wrong with his claim, "No man is an island"?
Island or no island, the waters all around us do seem to be shifting.