Lots of folks wonder if they are Jewish. It may be that they feel an inner pull toward Judaism and Jewish people. Perhaps they took a DNA test. It may be that there was a secrecy among the older generation that leads them to believe that the family tree is more tangled (and fruitful) than what meets the eye. It may be an unusual family name or unusual family traditions. Or it may just be curiosity. So how are we to determine who is Jewish, and what are we to do with the information once we have it?

The Basics Judaism is passed on exclusively through the biological female line. This means that if you trace your Jewish lineage through your mother’s mother’s mother’s mother (etc.), you are Jewish, even if all other branches of your family are not Jewish. (On the flip side, if your maternal line leads to a non-Jew, even if you live in New York, eat bagels with a schmear, and are deathly afraid of dogs, you are not a Jew.) But Judaism is not only conferred by blood. If you convert to Judaism under the auspices of a bona fide Orthodox beit din (ecclesiastical court), you are 100% Jewish, and so are all offspring born to you after your conversion (if you are female).

In Practice If you have been living as a Jew as part of the Jewish community for your whole life (as has your biological family for as long as anyone knows), it is safe to assume that you are Jewish. The same would apply to someone who either converted or is the direct descendant of a (female) convert. If you have been living as a non-Jew and wish to establish your maternal Jewish heritage, you may need to provide more evidence than “I once asked Aunt Charlene if we were Jewish and she stared back at me blankly.” As you can read here, genetic testing would not be sufficient either. It’s not that the Jewish community is hostile toward people who’ve dropped their tribal affiliation for a generation or two. It’s just that they want to make sure that you are indeed a member of the tribe before establishing you as such. Chances are that you’ll need to dig for old documents (or a Jewish person who can actually testify about your ancestor’s Jewishness). The exact type of documents needed can vary widely. For example, in Russia, Jewish people had their ethnicity written in their passports. The problem is that the Russians sometimes considered the children of male Jews to be Jewish. In addition, many people purposely got rid of the dreaded “fifth line” in their passport, since systemic anti-Semitism made it hard for Jews to advance in Soviet society. Thus, the passport of a great-grandmother who was born before intermarriage became common would possibly be a good piece of evidence. In some parts of Canada, legally-recognized birth records were typically kept by synagogues until the 1990s. Thus, a record of birth or marriage from an Orthodox synagogue would be very significant. In the U.S., by contrast, synagogues did not keep such good records, and whatever was recorded often disappeared when old congregations closed. There is a much smaller chance of finding a conclusive document of Jewish identity deep in an archive there. There are rabbis and rabbinical courts that specialize in documentation from various parts of the world. Rabbis who have experience in this field may often be skeptical. Experience has taught them that documents can be forged, and they have learned to ask hard questions and dig deeply before conclusively identifying a person as Jewish. But that should not stop you from digging. After all, if you do not look, the odds of finding anything are even smaller. If you discover Jewish ancestry deep in maternal past, but have been living as a non-Jew, it is customary for you to dip in the mikvah, not as a conversion (since you already are Jewish), but to symbolize a clean break from your non-Jewish past.

I’m Jewish, Now What? For some folks, discovering that they are Jewish is mind-blowing. They suddenly need to become part of an unfamiliar community and learn a new culture, belief system and way of life they may not even have known existed. The good news is that you can and should take it slowly. Get out a few books from the library, sign up for some emails from Chabad.org, and get to know the folks at your closest Chabad House. G‑d knows you well (after all, He created you). He does not expect you to scale the wall in one day. Grow a bit in your Jewish knowledge every day, and add slowly but surely to your Jewish observance. Gradually, you’ll feel more and more an integral member of the Jewish community. It may take a year. It may take a decade. But there will come a time that you’ll look around yourself and say, “Yes, this feels like home, and I am comfortable here.”

What Happens If You Draw a Blank? There are some folks who have good reason to believe that they are Jewish but lack the documentation to prove it. If you are such a person and you are truly committed to living a Jewish lifestyle (Shabbat, kosher, etc.), you may undergo what is known as giyur lechumra, a conversion just to be on the safe side. What happens if you discover that you have paternal Jewish ancestry or can uncover no concrete knowledge of a Jewish past at all? You have a choice. You can continue to live as a non-Jew with a special connection to Judaism and Torah. Living under the rubric of the 7 Noahide Laws, you can maintain (and grow in) your status as a good friend of the Jewish people even if you are not a Jew. And if you wish (and circumstances allow for it), you may choose to convert to Judaism. Only conversion done by a bona fide Orthodox beit din will achieve your goal, so make sure to do this one right. In very short, conversion consists of learning about and then accepting the Torah’s commandments, circumcision (for a male) and immersing in a mikvah, all under the guidance of the beit din. Note that once you convert, there is no going back. You’ll be obligated to live a full Jewish life, so make this decision carefully.