In 1973, “The Jewish Catalog” was published and became an unmatched phenomenon in American Jewish life, with sales soaring to over 300,000 copies.

Its three editors, Richard Siegel, Sharon Strassfeld and I, were part of Havurat Shalom, an intentional Jewish fellowship in Somerville, Massachusetts, where we studied Jewish texts, celebrated Shabbat with prayer and meals and explored what a contemporary Jewish life could look like. Emerging out of the Jewish counterculture of the time, we were eager to share our passion for creative Jewish life, and so the catalog was born.

“The Jewish Catalog” was an oversized paperback with essays, photographs, marginal comments and even little black-and-white cartoons. The aesthetic was definitely contemporary. The photos were mostly of young people with long hair, dressed in the bright clothing that was popular back then. We looked exactly like most other Americans.

The subtitle of the catalog was a “do-it-yourself” kit that tried to make Judaism accessible to its readers. It told you how to light Hanukkah candles and how to hang a mezuzah on your doorpost. It also suggested how to make your own Hanukkah candles and included a challah recipe.

More broadly, it encouraged people to practice a Judaism that didn’t rely on rabbis or other Jewish professionals to “do Judaism” for you. It invited people to take from the book what interested them. There was no list of what you needed to do to be a “good Jew.”

The catalog gave energy to changes that were already beginning to happen in American Jewish life. Many synagogues became more informal in style. Rabbis began to literally come down off the bimah/stage that separated the clergy from the worshippers. Synagogue music changed from cantorial pieces designed for listening to Jewish folk music that encouraged communal singing. Jewish religious life became more inclusive and egalitarian, particularly with respect to women. People began making their own tallitot and kippot, fueling a Jewish crafts movement.

Over the next 50 years, other elements emerged, including a focus on Jewish healing and Jewish spirituality. What the catalog essentially did was successfully capture the zeitgeist of America in the 1970s and translate it into a Jewish idiom.

It is apparent to me that the Judaism of the 20th century will not carry us in the 21st century.

My own story reflects that process. I grew up in a modern Orthodox home. I left that world for the Jewish counterculture and became a Reconstructionist rabbi at the age of 41. I continued to write books, hoping to make Judaism ever more accessible to Jews. Each book was different because the world had changed and I, too, had changed.

My new book, “Judaism Disrupted: A Spiritual Manifesto for the 21st Century,” follows this pattern. It is a result of my increased understanding that something important is happening in Jewish life as a result of modernity that requires major changes in Judaism. While “The Jewish Catalog” helped answer the question of how to be Jewish, my new book tries to answer a different question: Why be Jewish? Or, perhaps, why bother?

While Judaism seemed to thrive in the second half of the 20th century, liberal Judaism has begun to falter. Fewer liberal Jews are engaged in Jewish life by most measures. It is apparent to me that the Judaism of the 20th century will not carry us in the 21st century. The institutional structures that worked so well to acculturate us to American life — our federations, synagogues and JCCs, to name the most prominent — are struggling to succeed in the changing landscape, even as innovations begin to surface.

The picture is not all bleak. There are interesting emerging institutions. There are also existing institutions with exceptional leaders that are thriving. But overall, we are clearly in a disrupted period.

This is hardly the first seismic shift for Judaism. The transition from biblical Judaism to rabbinic Judaism must have felt like an earthquake to those who witnessed the destruction of the Second Temple in 70 C.E. Rabbinic Judaism developed over the next centuries, creating prayer and synagogues, a system of commandments and the religious leadership of rabbis. The genius of the rabbis was in creating a form of Judaism that was portable and could be carried wherever the winds of misfortune would carry the Jewish people in exile. For many centuries, this approach has formed the core of Jewish life.

Fifty years after “The Jewish Catalog” was published, the world is very different. I believe we now need a Judaism that is not just portable but permeable — that is, open to the world and able to respond fully to an open society that strives to be ever more inclusive. We no longer live in ghettos. The context for our Judaism is radically different. We not only interact with the world around us. The people of the world are increasingly members of our families.

The Judaism of the 21st century needs to provide wisdom and practices to take the most precious gift we have been given — our lives — and live them with purpose and meaning. Judaism isn’t about being a good Jew. It is about being a good person.

“Judaism Disrupted” suggests transforming rituals into awareness practices that remind us of who we want to be, whether that involves a brief daily morning practice to frame our day or practices that help us cultivate such inner qualities as gratitude, generosity and satisfaction. It offers new practices and reframes traditional practices as regular parts of our lives. It challenges us to discard some traditional practices or radically alter them, such as traditional prayer services, which seem to leave too many people feeling unengaged.

What does it mean to be a Jew in the 21st century? In part, it means being a mensch: living with the awareness that we were strangers in Egypt and therefore we need to take care of those on the margins of society. Being a mensch also describes how we interact with family and friends, recognizing both that we are all images of God and that everyone is an imperfect human.

But being a mensch isn’t enough. To lead a full Jewish life, we must become spiritual menschen, feeling connected to something larger than ourselves. We must feel connected to this planet, to God or to the oneness/wholeness that underlies the universe. Just as “The Jewish Catalog” was a response to the challenges of a half-century ago, “Judaism Disrupted” is a response to the challenges of our time. My deepest wish is that it provokes serious conversation and new ideas.