Journalist Rosenbaum’s In Defense of Love (Doubleday, Aug.) investigates the enigmatic phenomenon and debunks theories that seek to quantify it.

When did you decide that love was in trouble?
In the ’80s my editor at Esquire, Betsy Carter, told me about a song that actors and actresses play to prepare for crying scenes on set—“Long Long Time” by Linda Ronstadt. I listened and was just completely knocked out. It made me think that there are hundreds of songs with great chords and voices, and yet there are only a few that have a magic to them. I interviewed Ronstadt and other great writers of love songs trying to figure out what enabled them to reach that realm. I still haven’t found an answer to it, but what I have found is my own antipathy to people who think they’ve solved it. What motivated the book was a polemic against those who want to flatten these moments of great artistry and mystery into algorithms.

You describe reductionists as threats to love. Who are they and what are they trying to achieve?
They are people who are claiming to have solved the great mystery of love. I’ve gradually seen more and more attempts in neuroscience, anthropology, and genetics. Have you heard of histocompatibility? It’s a genetic theory that says people are attracted to each other because they have different antigen types, and by coming together they expand their immunity. I began to think more about theories like this and how culture has a craving for numerical explanations of mysterious or hard-to-explain phenomena. It’s like the five stages. It started out with grief and mourning, but now you’ll see the five stages of just about anything. I think people deal with a fear of the unknown by trying to create predictable steps.

Why did you choose to write about your own romantic experiences?
I had written about what is being done to love, and I felt a responsibility to not pretend to be above the battle. I wanted to give a couple examples of what love has done to me and what I’ve learned. I’ve learned a lot about myself and my relationships. One woman I dated was diagnosed with cancer and told me she was about to die. That taught me how to treasure every moment with someone. Another woman observed that my relationships often didn’t last longer than a couple of years. It sent me into a long process of introspection from which I learned more about myself and felt more ready to do the things that led to the relationship I’m in now, lasting seven years so far.

What do you want readers to take away from this book?
That love remains a fathomless mystery that they’re not going to solve. They’re just going to have to experience it.