Classical Judaism holds that there is a dual Torah, consisting of the Torah Sh'b'ktav (the Written Torah) and the Torah Sh'Ba'al Peh (the Oral Torah). Commandments derived from the written Torah are called "d'Oraita" from the Aramaic word meaning "from the Torah."

For traditional Judaism, the Oral Torah consists of Oral Torah revealed simultaneously at Sinai as well as enactments, laws, and interpretations instituted by later rabbis (d'Rabbanan). The basis or authority for the laws classified as"d'Rabbanan" and for the implementation of the observance of the commandments is derived from Deuteronomy 17:8-11.

The rabbis claim that the authority to interpret the commandments and subsequently define (i.e. the way in which the commandments are observed) is found in the written Torah itself, where Moses states that any case or question too difficult for the Jewish people in future days should be brought before the priests and judges in office at that time.

To this day, the rabbis serve as judges and legislators akin to a court and a legislature. Rabbis are in fact dayanim (i.e. Judges). The written Torah serves as the constitution for Israel with the Oral Torah and the Rabbis serving as the legislative process. Like the Constitution of the United States, the implementation of its statutes are left to the Congress and the validity of those laws is left to the courts. The concept of a constitutional model for Torah law that "evolves" or is "pliable" allows it to remain relevant and applicable.

A Torah model that does not include this eventually creates a situation in which many biblical commandments cannot be observed, applied, or understood. Hence a community like the Karaites who argue that they follow only the Biblical text have almost reached the point of extinction, have isolated and in fact excluded themselves from the Jewish community by adopting different calendar and different laws. In the end they nevertheless created a body of their own "halachah"out of necessity in attempting to follow the written text.

The case or argument for the Oral Torah exists on two levels. On a very basic level, the very necessity of Oral Torah can be established by looking at the text of the Torah itself.

The a Torah scroll is written only with consonants, without vocalization. Hence one word written in Hebrew can have multiple meanings. Hence, where the Hebrew text says "BNCH," one might render this as "Bonayich" "your Builders" or as "B'nayich" "your Children." This occurs quite often. Vowels marks were only added much later after the text was written and codified.

So even the ability to read and understand the biblical text is based upon an oral tradition which grants us the ability to pronounce the alphabet, to read, and most importantly understand the text.

The famous Hillel was approached by a non-Jew who desired to learn the Torah on the condition he would learn the written Torah only. He started teaching him the alef-bet and the next day changed the names of the letters and their pronunciation and the student was confused. He did this to prove a point!

The text is foundational but it is informed and understood only with the aid of the oral tradition.