So, when was the last time that you worshiped with five thousand Jews at a Shabbat morning service?

The answer is: never.

The biennial convention for the Union of Reform Judaism (URJ), the Reform movement, which ended yesterday, was the largest in recent memory — as Reform Judaism is the largest American Jewish denomination.

To be in the presence of thousands of Reform Jews, with our enthusiasm and commitment, was to encounter something powerful.

Anyone who attended this biennial convention would have left with the impression that the single largest item on Reform Judaism’s agenda is social justice (with our youth and camping programs a very close second).

Social justice was the constant theme of the special presentations during the plenary sessions. We heard from such luminaries as Senator Elizabeth Warren and Reverend William Barber, who moved me like no other preacher since Martin Luther King. They brought the assembled throngs to their feet.

So, by the way, did Governor Charlie Baker of Massachusetts, who is a Republican (and kudos to the URJ leadership, for knowing that we have to reach out to Reform Jewish Republicans, which, it turns out, is not such an oxymoron).

Let me be clear. The social justice component of this movement is crucial to me, and to many of my people.

My congregation, Temple Solel in Hollywood, Florida, has taken a national leadership role in raising consciousness about Sea Level Rise and other climate change issues. Ours was the lead congregation in bringing a resolution on that subject to the floor of the biennial.

But, any number of my colleagues walked away from the biennial convention, and they asked themselves that old Peggy Lee question: “Is that all there is?”

The “that” is social justice.

Reform Judaism’s emphasis on social justice is an essential part of its identity. Its outward gaze is natively Jewish, for we are forbidden to pray in a sanctuary that does not have windows.

But, taken to extremes, and privileging that commitment above everything else, it reminds us of another piece of our classical Reform legacy — that the essence of Judaism is ethics, and therefore, social justice, which is ethics writ large.

That allowed us to think that we are just like everyone else — or, at least, like all other good people.

Except, to quote that old Levy’s rye bread ad: You don’t have to be Jewish to be ethical.

Nor, to care about racism, gun control, etc.

For, if Jews were to suddenly disappear from those causes, those causes would still survive.

But, if we stopped caring about Shabbat, the search for kedusha (holiness), prayer, and Jewish literacy — what, then, would happen to the Jewish people, and to Judaism?

Social activism is virtuous.

But, it requires no specific Jewish skills. Not a word of Hebrew. What does this say about the curriculum of Reform Jewish life?

We love to quote Rabbi Abraham Joshua Heschel, who, at Selma, said that he was “praying with his feet.”

But, that morning, Heschel had already prayed — with a siddur.

The deeper question is: what matters to Reform Jews? What are we not paying attention to?

Go back to the 2013 Pew Center report on American Judaism.

Reform Jews (or, those who identified themselves as Reform Jews; we do not know if they are members of Reform congregations, or, doing little or nothing, simply imagine themselves to be Reform Jews, which is a huge part of the problem) cited the following as essential to their Jewish identity.

• Remembering the Holocaust 77 percent
• Leading an ethical life            75 percent
• Working for justice and equality     62 percent
• Being intellectually curious      52 percent
• Caring about Israel                 42 percent
• Being part of the Jewish community 25 percent

The 42 percent of those Reform Jews who cite “caring about Israel” as an essential part of their Jewish identity is the lowest of any denomination. That’s a problem.

So, tellingly, is “being part of the Jewish community.” That’s also the lowest of any denomination. That’s an even bigger problem.

“Intellectually curious?”

Wait a minute.

Didn’t we Reform Jews always pride ourselves on our depth, on the need to study the Jewish sources in order to make intelligent Jewish life choices?

Have we so vigorously assimilated into American life that we are now anti-intellectual, which is the dark side of American exceptionalism?

News flash. By every conceivable measuring tool, Reform Jews simply do “less Jewish” than other Jews.

Here’s why. Reform Jews have accepted the premises of modernity more than any other Jewish group.

• When it comes to individualism and choice, the hallmarks of modernity, we are the strongest.
• When it comes to community and communitarianism, the hallmarks of Judaism, we are the weakest.

All of which brings us to a vulgar folk ideology in which Reform Jews say: “I don’t want to. You can’t make me.”

In that sense, American Reform Judaism has failed to create a generation of Jews who have cultivated, in the words of sociologist Robert Bellah, Jewish “habits of the heart.”

Here is what keeps synagogue leaders — clergy and lay — awake at night:

• In many places, demographic challenges have forced synagogues to shrink.
• Synagogue finances face challenges.
• We have not yet cultivated a new generation of lay leaders who will make our synagogues come alive.
• Five thousand Reform Jews at a Shabbat morning service is great. On any given Sunday, go to any mega-church in America, and that same number will be there. Reform Jews are the Americans who are least likely to attend a religious service.
• American consumerism threatens Judaism — with its emphasis on the trendy over the tried and true, and on expediency over commitment.

Will social activism “save” the next generation of Jews for Judaism?

We don’t know — yet.

But, I will say this.

There is no movement as responsive to American Jewish challenges as the Reform movement.

Neither is there any American Jewish leader with the capabilities as Rabbi Rick Jacobs, the president of the URJ.

A movement with that kind of competence, leadership, and ambition can totally re-invent Reform Jewish commitment.

There are many Reform Jews out there who are ready to help make it happen.