“I want earth, not heaven,” concludes Mary Johnson in the epilogue to her spellbinding memoir, An Unquenchable Thirst. In the book, she describes her spiritual calling to work with Mother Teresa, along with the inner reckonings that compelled her to leave a nun’s life and her faith after 20 years in the convent.

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After Johnson took one look at Mother Teresa on the cover of Time in 1975, the devout then-17-year-old Texan knew that she not only wanted to devote her life to God but work alongside the pious, world-renowned champion of the poor. At 19, Johnson joined Mother’s order, the Missionaries of Charity, soon becoming Sister Donata, and spent the next two decades serving the needy in the United States, Canada and mostly in Italy, all the while grappling with the Missionaries’ political underpinnings and her inner desires for companionship and autonomy. 

The struggle Johnson outlines in her ravishingly intimate account is reminiscent of The Confessions of St. Augustine, and her walking away from the order in 1997, just months prior to Mother Teresa’s death, has yielded a most passionate love story of self-discovery. We talked with Johnson, eager to learn more about this magnum opus that was a decade in the making.

When did you decide to write this?

I think I always kind of knew that I had a story to tell. When I would tell people that I had been a nun for 20 years and left, they were always like, “Oh, I want to know more. You should write a book.” 

I think I really started to take the idea seriously, though, when my younger sister phoned me. I’d been out of the convent maybe two years when she phoned and said that she was getting married that weekend because her guru had cleared her to marry a fellow she’d met twice. I said, “You don’t know this guy.” And she said, “No, the guru said it’s all going to be fine.”

Somehow I realized if I could write a book and tell my story in such a way that people could come to realize the dangers of giving away your own common sense, your own autonomy to any sort of spiritual authority—no matter how good that person might be—it would be a good thing if I could make people think twice before doing that.

What fears did you have to overcome to tell your tale with such candor?

The fear of getting it down on the page was the first fear, and the second fear was what will people think—what will my family think, what will my friends think, and then what will the Sisters think, because a lot of the Sisters didn’t have any idea of all the things that were going on, and not just things that I did, but things that other Sisters did.

I’m telling my story, but it involves other people also, and it gets very tricky because the other people are there—they’re important to your story. There are things that really happened, but at the same time, how much can you really tell? I decided to tell the things that were important to my story and to sort of let the other things go. I didn’t go into a lot of detail from anyone else’s perspective. I just chose to tell the stories and the changes that happened in me.

There are so many poignant moments you describe. One that got me: it’s Rome, 1987, you’re nearly 28, and you’re sharpening a pencil with a razor blade. What do you feel looking back on that now?

I suppose I miss the simplicity of that life. That was one of the things, you know, we made do with very little. And while sometimes that could be very hard, it was also very liberating in many senses. You never had to worry about what you were going to wear. It was always the same—these decisions were already made.

There’s something very pure, perhaps, about a simple life unencumbered by a lot of things. It’s still kind of very appealing. You know, I’m not sharpening my pencils with razor blades any longer, there are certain things I do with a computer. But there’s a part of me that still misses some of that simplicity, I think, just being able to do things with very little.

Mother Teresa wrote, “The loneliness of the heart that wants love is unbearable,” and one of the themes in the memoir that comes across so strongly is what the lack of a friend can do to you and how that need for intimacy is so vital.

Exceedingly vital—it’s what makes life worthwhile sometimes, you know. I think it’s part of what Mother talks about in being lonely and that experience she must have had, of being incredibly lonely even though she was always surrounded by people. How painful that must have been for her. I feel very bad. I have this kind of ache in my heart. It’s just really sad.

A pivotal scene toward the end of the work is your final audience with Mother, where she’s banging on the table, imploring you to answer, “Why do you want to go?” Is this book the confession you refused to give her that day? 

Yeah, I think that’s part of it. I do. That’s very insightful, a way of explaining to her and to myself and to anyone who wants to know why I left, why I joined, why I stayed, what happened to me. It was a way of giving myself the time and space I needed to explore those questions for myself in a very deep way. Certainly I could have done that without writing a book, but I also think I’m a person for whom writing has always been important. It’s kind of always been the way I’ve processed things.

Do you mind talking about what you’ve written?

One of the reasons I wrote—I’m very clear on this—is people don’t talk about these things. All sorts of things go wrong with priests and sisters, and nobody is willing to talk from their own experiences, or very few people are—and certainly not publicly in a way that would, perhaps, embolden other people to tell their own stories. 

And I just think it is very important that a lot of people start telling their stories. It’s just very odd to hear, what it should be, what it should be, and getting lost in theologizing all sorts of things. I think in the Church people have been avoiding talking about reality for a long time, and I hope that putting my story out there will help others tell their stories.