Jewish identity is due to matrilineal descent, meaning the Mommy determines the child’s identity—Jewish or not.

This law comes from the Torah¹, which is the constitution and deciding factor for Judaism. 

One of the reasons offered to explain this is law is though both parents contribute to the genetic make-up of a child, the father’s involvement in conceiving the child is fleeting compared to the pregnancy and birth that the mother experiences. Clearly the mother’s involvement in the child’s formation is incomparably greater than the father’s.

Furthermore, much has been scientifically demonstrated that aside from genetic make-up, a baby is greatly influenced by the conditions of the womb, and these factors have long-term effects on that person. So even before birth, a baby’s life-long being is deeply bound with that of his or her mother. All this considered, it is no surprise then that the very essence of the child – who he or she will be – is determined by the mother. Whether a child is Jewish or not is not a minor detail of the child’s composition, it is a question of his or her very identity—thanks to Mom.

Whether a child is Jewish or not is not a minor detail of the child’s composition, it is a question of his or her very identity—thanks to Mom

All three tribal divisions have the common essential factor of being Jewish, as determined by the mother. The difference in these three is their function— their Jewish job-description. A Kohen, Levite and Israelite each have his (or her) unique spiritual profession, whether it be in the Temple or in the office. This secondary identification is passed on through the father.

[In the case of a person born of a Jewish father and a non-Jewish mother, the tribe association is irrelevant since the child is not Jewish. In the reverse situation—Jewish mother and non-Jewish father—the child is Jewish and a (tribe-less) Israelite.]