The "Who is a Jew" issue has become one of the most controversial issues in Jewish life today.
Matrilineal descent, the passing down of a child's Jewish identity via the mother, is not a biblical principle. In biblical times, many Jewish men married non-Jews, and their children's status was determined by the father's religion.
According to Professor Shaye Cohen of Brown University:
"Numerous Israelites heroes and kings married foreign women: for example, Judah married a Canaanite, Joseph an Egyptian, Moses a Midianite and an Ethiopian, David a Philistine, and Solomon women of every description. By her marriage with an Israelite man a foreign women joined the clan, people, and religion of her husband. It never occurred to anyone in pre-exilic times to argue that such marriages were null and void, that foreign women must "convert" to Judaism, or that the off-spring of the marriage were not Israelite if the women did not convert."
Sometime during the Roman occupation and the Second Temple period, a law of matrilineal descent, which defined a Jew as someone with a Jewish mother, was adopted. By the 2nd century CE, it was clearly practiced.
The Talmud (Kiddushin 68b), which was compiled in the 4th and 5th centuries, explains that the law of matrilineal descent derived from the Torah. The Torah passage (Deut. 7:3-4) reads: "Thy daughter thou shalt not give to his son, nor shalt thou take his daughter to thy son. For they will turn away thy son from following me, that they may serve other gods."
Some scholars believe that this new law of matrilineal descent was enacted in response to intermarriage. Others say that the frequent cases of Jewish women being raped by non-Jews led to the law; how could a raped Jewish woman's child be considered non-Jewish by the Jewish community in which he or she would be raised? Some believe that the matrilineal principle was borrowed from Roman law.
For centuries, while orthodox Judaism was the only form of Judaism, the law of matrilineal descent was unquestionably accepted. Orthodox Judaism even believed that anyone with a Jewish mother had irrevocable Jewish status; in other words, even if someone with a Jewish mother converted to another religion, that person would still be considered Jewish.
With the birth of alternative branches of Judaism and the rise in intermarriage in the 20th century, questions about the law of matrilineal descent arose. Children born to Jewish fathers and non-Jewish mothers, in particular, were asking why they were not accepted as Jews.
In 1983, the Reform movement made a Patrilineal descent ruling. The Reform movement decided to accept the children of Jewish fathers as Jews even without a conversion ceremony. In addition, the movement decided to accept people who were raised as Jews, such as adopted children, even if it was not certain that either of their parents were Jewish.
Reconstructionist Judaism, which values equity and inclusivity, also adopted the idea of patrilineal descent. According to Reconstructionist Judaism, children of one Jewish parent, of either gender, are considered Jewish if raised as Jews.
In 1986, in contrast, the Conservative Movement's Rabbinical Assembly reiterated the commitment of the Conservative movement to the law of matrilineal descent. Furthermore, the movement stated that any rabbi who accepts the principle of patrilineal descent will be subject to expulsion from the Rabbinical Assembly. While the Conservative movement did not accept patrilineal descent, it agreed that "sincere Jews by choice" should be warmly welcomed into the community and that "sensitivity should be shown to Jews who have intermarried and their families." The Conservative movement actively reaches out to intermarried families by offering them opportunities for Jewish growth and enrichment.
As of today, Judaism is divided on the issue of "Who is a Jew?" via descent. Orthodox Judaism stands unequivocably behind Judaism's almost 2000 year old law of matrilineal descent. Conservative Judaism has stayed loyal to the traditional matrilineal descent law, but, compared to Orthodoxy, is more open in its acceptance of potential converts, more sensitive in its approach to intermarried Jews, and more active in its outreach to intermarried families. Reform and Reconstructionist Judaism have expanded their definition of a Jew from one with a Jewish mother to also include one with a Jewish father.