In 2006, i was 50—and I was falling apart.

Until then, I had always known exactly who I was: an exceptionally fortunate and happy woman, full of irrational exuberance and everyday joy.

I knew who I was professionally. When I was 16, I’d discovered cognitive science and analytic philosophy, and knew at once that I wanted the tough-minded, rigorous, intellectual life they could offer me. I’d gotten my doctorate at 25 and had gone on to become a professor of psychology and philosophy at UC Berkeley.

I knew who I was personally, too. For one thing, I liked men. I was never pretty, but the heterosexual dance of attraction and flirtation had always been an important part of my life, a background thrum that brightened and sharpened all the rest. My closest friends and colleagues had all been men.

More than anything, though, I was a mother. I’d had a son at 23, and then two more in the years that followed. For me, raising children had been the most intellectually interesting and morally profound of experiences, and the happiest. I’d had a long marriage, with a good man who was as involved with our children as I was. Our youngest son was on his way to college.

And then, suddenly, I had no idea who I was at all.

My children had grown up, my marriage had unraveled, and I decided to leave. I moved out of the big, professorial home where I had raised my children, and rented a room in a crumbling old house. I was living alone for the first time, full of guilt and anxiety, hope and excitement.

I fell in love—with a woman, much to my surprise—and we talked about starting a new life together. And then my lover ended it.

Joy vanished. Grief took its place. I’d chosen my new room for its faded grandeur: black-oak beams and paneling, a sooty brick fireplace in lieu of central heating. But I hadn’t realized just how dark and cold the room would be during the rainy Northern California winter. I forced myself to eat the way I had once coaxed my children (“just three more bites”), but I still lost 20 pounds in two months. I measured each day by how many hours had gone by since the last crying jag (“There now, no meltdowns since 11 this morning”).

I couldn’t work. The dissolution of my own family made the very thought of children unbearable. I had won a multimillion-dollar grant to investigate computational models of children’s learning and had signed a contract to write a book on the philosophy of childhood, but I couldn’t pass a playground without tears, let alone design an experiment for 3-year-olds or write about the moral significance of parental love.

Everything that had defined me was gone. I was no longer a scientist or a philosopher or a wife or a mother or a lover.

My doctors prescribed Prozac, yoga, and meditation. I hated Prozac. I was terrible at yoga. But meditation seemed to help, and it was interesting, at least. In fact, researching meditation seemed to help as much as actually doing it. Where did it come from? Why did it work?