an ethnicity, a religion, or peoplehood, the definition depends on either traditional or newer interpretations of Jewish law and custom. Israel's Law of Return stipulates that a Jew is someone with a Jewish mother or someone who has converted to Judaism and is not a member of another religion. The Israeli Chief Rabbinate requires documents proving the Jewishness of one’s mother, grandmother, great-grandmother and great-great-grandmother when applying for marriage. The Office of the Chief Rabbi (OCR) has underlined the basic principle that a child is not recognised by the OCR and other bodies as Jewish unless their mother is Jewish, or they underwent a conversion recognized by the body. According to the simplest definition used by most Jews for self-identification, a person is a Jew by birth or becomes one through religious conversion. However, there are differences in interpretations when it comes to non-Orthodox Jewish denominations in the application of this definition, including Should a person with only a Jewish father be considered Jewish? Which conversion processes should be considered valid? Can one remain a Jew after converting to another religion? How does being unaware of having Jewish parents affect one's Jewish status? How is Jewish identity determined in different countries throughout the Jewish Diaspora? How is the claim to Israeli citizenship adjudicated in the context of the Basic Laws of Israel? Tannaitic Judaism According to the Mishnah, the first written source for halakha, the status of the offspring of mixed marriages was determined matrilineally. According to historian Shaye J. D. Cohen, in the Bible, the status of the offspring of mixed marriages was determined patrilineally. He brings two likely explanations for the change in Mishnaic times: first, the Mishnah may have been applying the same logic to mixed marriages as it had applied to other mixtures (kilayim). Thus, a mixed marriage is forbidden as is the union of a horse and a donkey, and in both unions the offspring are judged matrilineally. Second, the Tannaim may have been influenced by Roman law, which dictated that when a parent could not contract a legal marriage, offspring would follow the mother. Contemporary Judaism All Jewish religious movements agree that a person may be a Jew either by birth or through conversion. According to halakha, a Jew by birth must be born to a Jewish mother. Halakha states that the acceptance of the principles and practices of Judaism does not make a