More than 20 years ago, as an undergraduate at Princeton University, I found myself rooming with a bright, young religious Lutheran from Iowa. It was, to be sure, a somewhat unusual mix, and he never could quite comprehend why I was rushing off to prayer services every day or checking the ingredients on various food packages. But he was a cosmopolitan and studious sort, one whose desk was constantly piled high with books, and his curiosity about the world and impressive intelligence often made for some intriguing conversations.

So when I asked him once how many Jews he thought lived in America, I was more than a little stunned when he insisted, in all seriousness, that "there must be at least 50 million Jews in this country." Asked to explain the basis for his calculation, my friend shrugged and told me, "Well, I grew up in a town in middle America, and our family doctor was Jewish, my dad's lawyer was Jewish and so was his accountant. And," he added," there are so many prominent Jews in various fields, that there simply must be 50 million or more of you guys out there." Only after I showed him a reference book which listed the world Jewish population at approximately 13 million, was he satisfied that his estimate had been wide of the mark.

I often reflect back on that conversation, as it touched on key questions such as the perception of Jews, our role in society and the impact that we as a people have on the world. But I think that it also raises still another, perhaps even more compelling issue, one that is rarely if ever addressed with the seriousness that it deserves: does it matter how many Jews there are in the world?

Traditionally, of course, we have never placed a great deal of emphasis on the size or dimensions of the Jewish people. For the past 2000 years, living at the mercy of others, we tended to focus more on quality rather than quantity. That, quite possibly, is why many Jews tend to discount or minimize the importance of our numbers, arguing that what really matters is whether we are working effectively to fulfill our national destiny.[i]

But I believe this mode of thinking is a product of exile, a function of the fact that we were more concerned with surviving, rather than thriving, during the long, dark night of our wanderings in foreign lands. In the process, we tended to lose sight of the important role that numbers can and do play in the life of a nation. And we have even gone so far as to elevate our numerical weakness into a value, infuse it with meaning, and now hold it up as the ideal.

Neither Jewish sources nor Jewish history justify this view, and it is time that we revisit the question, not merely because it is an interesting intellectual exercise, but rather due to the critical importance that it has to shaping our community's policies, future and world-view.

It is a well-known principle of Jewish belief that the Creator chose the Jewish people to be His unique instrument in this world. "And you shall be unto Me a kingdom of priests and a holy nation,"[ii] God instructs Moses to tell Israel just prior to giving them the Torah at Mount Sinai.

Later, in the book of Devarim, Israel's special relationship with God is described in even more intimate terms: "You are the children of the Lord your God… you are a holy people to the Lord your God, and the Lord has chosen you to be His own treasure out of all peoples that are upon the face of the earth"[iii].

From these verses, it is clear that God did not choose a family or a small tribe to serve His purposes in this world. He chose an entire nation, the people of Israel. Obviously, then, a critical mass is essential to carry out our sacred mission, for if it were not, then He could easily have placed the responsibility on just a handful of shoulders.

In other words, numbers do matter. Critics often assail this line of thinking, asserting that quantity without quality is of little value in ensuring the Jewish future. But what they fail to realize is that the opposite is equally true. A tiny and shrinking Jewish people, consisting only of a small core of committed members, will hardly be able to meet the challenges and threats to our survival, be they physical or spiritual.

And that, perhaps, is why God promised the patriarchs, Abraham, Isaac and Jacob, that the Jewish people would one day be as numerous as the stars in the sky or the sand by the sea. For only then can we possibly be in a position to fulfill our role.

Indeed, even a cursory look at the Torah and the commentaries reveals that the demographic prowess of the Jewish people is repeatedly emphasized in God's pledges to our forefathers.

"And I will make your seed as the dust of the earth," God assures Abraham, telling him, "so that if a man can number the dust of the earth then so shall your seed also be numbered".[iv] Rashi understands this promise to be literal, not metaphorical. He explains the verse as follows: "Just as the dust cannot be counted, so too shall your seed be beyond counting."[v]

Similar pledges were made to Isaac and Jacob,[vi] and when Moses addressed Israel before his death, he too prophesied that God would multiply them "a thousand times over".[vii] This, says the Netziv, is a promise that relates both to the quality and quantity of the Jewish people.[viii]

Over a millennia later, during the Herodian period, the Jewish people had in fact grown to be a sizeable force on the world stage. As historian Paul Johnson has pointed out,

One calculation is that during the Herodian period there were about eight million Jews in the world, of whom 2,350,000 to 2,500,000 lived in Palestine, the Jews thus constituting about 10 percent of the Roman empire. This expanding nation and teeming diaspora were the sources of Herod's wealth and influence.[ix] (emphasis added)

It is interesting to note that at around the same time, what historians have described as the earliest preserved census in the world was taken in China, in the eighth month of the year 2 C.E.[x] It found that there were a total of 57.5 million Chinese, or seven Chinese for every Jew then living.

Jump ahead 2000 years to the present, and the numbers are of course quite different, with China having soared to more than 1.1 billion people, even as world Jewry barely numbers more than 13 million souls.

Needless to say, the difference is attributable to all the expulsions and persecutions that have been our lot, which have shorn away untold numbers of Jews from our ranks, leaving just a small remnant of what might have been.

This sad reality was brought into even sharper focus last year, when distinguished demographer Sergio Della Pergola of the Hebrew University released a chilling study which concluded that had it not been for the Holocaust, there would be 32 million Jews in the world today.[xi]

The Holocaust, he wrote, had "struck a mortal blow particularly at the Jews of Eastern Europe because of their especially young age structure." This, he said, had caused "significant long-term demographic damage" with ramifications "far beyond what we think."

Indeed, as Della Pergola pointed out, the percentage of Jews in the world today is steadily declining. Whereas prior to World War II, there were eight Jews per thousand people in the world, the figure now stands at just two per every thousand, and it is heading southward.

The findings are a timely and distressing reminder of the unfathomable destruction which the Holocaust wrought. Not only did it claim the six million who were murdered by the Germans and their collaborators, but it also took away their children, grandchildren and all of their descendants, forever depriving the Jewish people of untold millions of precious souls. In other words, the scope of the killing, magnified over time, becomes ever more extensive and incomprehensible.

Just imagine a world in which a vibrant and ample Jewish people, more than double its present size, were not beset by the constant threat of demographic diminution and assimilatory attenuation.

Consider for a moment the cultural and spiritual riches that we would be producing, the mighty intellectual and cerebral contributions to mankind that we could be making, and you begin to realize the extent of what has been lost.

SOMEHOW, while we were getting collectively beaten up in the Diaspora over the centuries, we seem to have moved away from this approach. But now might be just the time to start rethinking it. After all, size does matter, whether in basketball, business or international diplomacy. And to make a difference in the world and live up to our Divine national mission as Jews, we need a much larger and more diverse "team" at our disposal.

This means that we not only need to work harder at keeping Jews Jewish, but we also must expand our horizons and look for ways consistent with halakha to boost our numbers.

A good place to start would be with descendants of Jews, with communities that have a historical connection with the Jewish people and are now interested in returning. These include the Bnei Menashe of northeastern India, who are descended from a lost tribe of Israel, the Bnei Anousim of Spain, Portugal and South America (whom historians refer to by the derogatory term "Marranos"), the "Hidden Jews" of Poland from the Holocaust-era, as well as others.

Through no fault of their own, these people's ancestors were taken by force from the Jewish people, and we owe it to them and their descendants to embrace them and give them the opportunity to come home. Doing so will not only right a historical wrong, but it will strengthen us numerically and spiritually as well.

This is not a call to missionizing, nor a plea to start converting gentiles. It is about opening the door to our lost brethren, known as Zera Yisrael ("the seed of Israel"), and reinforcing the bond between us.

Take, for example, the Bnei Anousim, whose ancestors were forcibly converted to Catholicism during the 14th and 15th centuries in Spain and Portugal, but who continued to preserve their Jewish identity in secret down through the generations. Five centuries later, a growing number of their descendants are now emerging from the shadows, seeking to reclaim their long-lost Jewish heritage.

It is a phenomenon of unprecedented proportions, stretching from Lisbon to Lima and from Madrid to Mexico. People throughout the Spanish- and Portuguese-speaking world are now choosing to explore their families' Jewish roots, which were often buried under the weight of history.

The extent to which that legacy still lives on was underlined by the findings of a noteworthy paper published in the American Journal of Human Genetics in late 2008, in which a team of biologists declared that 20% of the population of Spain and Portugal has Sephardic Jewish ancestry.[xii] Since their combined populations exceed 50 million, that means more than 10 million Spaniards and Portuguese are descendants of Jews.

These are not wild-eyed speculations, but rather cold, hard results straight out of a petri dish in a laboratory. The study, led by Mark Jobling of the University of Leicester in England and Francesco Calafell of the Pompeu Fabra University in Barcelona, analyzed the Y chromosomes of Sephardim in communities where Jews had migrated after the expulsion from Spain in 1492. Their chromosomal signatures were then compared with the Y chromosomes of more than 1,000 men living throughout Spain and Portugal. Since the Y chromosome is passed from father to son, the geneticists were able to measure the two groups up against each other, leading to the remarkable finding that one-fifth of Iberians are of Jewish descent.

Think about it: it is as if a large mirror were suddenly being held up in front of every Spanish and Portuguese person, forcing them to look at themselves and see the reality of their national, and individual, history.

But even more compelling than what it says about the past is what it might just say about the future. If Israel and the Jewish people undertake a concerted outreach effort toward our genetic brethren in Iberia, it could have a profound impact in a variety of fields. The very fact that such large numbers of Spaniards and Portuguese have Jewish ancestry could have a significant effect on their attitudes toward Jews and Israel.

As Chairman of Shavei Israel, which works with "lost Jews" around the world, I have seen it time and time again - when a person discovers, or rediscovers, their Jewish roots, they inevitably develop a certain affinity to the Jewish people and a greater sympathy for Israel and Jewish causes. Obviously, not all of the millions of people of Jewish descent will rush to convert back to Judaism or seek to make aliyah. But some undoubtedly will return to our people and strengthen our ranks.

The idea that such "lost Jews" will ultimately return is both long-standing and deeply-rooted in Jewish thought, even if most of us may not realize it.

Take, for example, the prophet Isaiah's vision that, "It shall come to pass on that day, that a great shofar will be blown and they that were lost in the land of Assyria shall come and they that were dispersed in the land of Egypt, and they shall bow to God on the holy mountain in Jerusalem".[xiii] According to Rashi, the first part of the verse - "they that were lost in the land of Assyria" - means those "who were dispersed far beyond the Sambatyon river"[xiv], a reference to the Ten Lost Tribes of Israel who went into exile more than 2700 years ago.[xv] In other words, their descendants, despite being lost for so many centuries, will in fact come back.

The same holds true for the Bnei Anousim. The great Don Isaac Abarbanel, who witnessed the expulsion of the Jews from Spain in 1492, writes movingly in his commentary to Sefer Devarim that many of the Bnei Anousim "shall be mixed in among them [i.e. the nations] and considered like them, but in their hearts they will return to God…. and those who leave the religion [i.e. Judaism] because of compulsion, about them does it say, 'and He will return and gather you from among the peoples'".[xvi]

The illustrious Rabbi Tzadok HaKohen of Lublin goes even further, stating that all descendants of Jews will one day return to our people. In his work Resisei Layla, he writes that this includes even those who are of Jewish descent but do not know it: "for everyone who is from the seed of Israel, none shall be banished".[xvii]

From its very inception, the nation of Israel was divided into 12 tribes, each with its own unique traits, talents and blessings. God, in His ultimate wisdom, deemed it necessary for our people to be forged into unity through diversity, like an orchestra comprised of different musicians, each playing his own instrument even as he follows the same book of music.

We are living in a world that is growing smaller by the day, thanks to the reach of the Internet. In order to thrive in this global village, we need Chinese Jews and Indian Jews and Polish Jews no less than American and Australian Jews. We are one nation, with many faces, and we have to learn to leverage our diversity and view it as a strength rather than a weakness. We might never be able to match China's demographics, but we can and should look for new opportunities for growth. That is why the time has come to undertake a concerted outreach effort to descendants of Jews.

Our precarious state as a people, and the threats we face at home and abroad, demand as much. And so, I might add, does our destiny.