It's important to clarify a common misconception many have about the Oral Torah in Judaism.
The Oral Torah is not an “after-thought” interpretation of the Written Torah. In fact, the giving of the Oral Torah actually preceded the giving of the written Bible we have today. When the Jewish people stood at Mount Sinai 3,300 years ago, God communicated the 613 commandments, along with a detailed, practical explanation of how to fulfill them. At that point in time, the teachings were entirely oral.
It wasn't until 40 years later, just prior to Moses' death and the Jewish people's entering the Land of Israel, that Moses wrote the scroll of the written Torah (known as the Five Books of Moses) and gave it to the Jewish people.
Why Do We Need an Oral Torah?
The story is told about a fellow who applies for a job at a prestigious investment banking firm. The interviewer looks at his resume and says, "I see you went to Harvard Business School. Very nice. Tell me, what year did you graduate?"
The fellow says, "1990."
"1990. Did you ever take any courses with Professor Stevens?"
"Okay, how about Professor Phillips? He's one of the most popular professors at Harvard. Older fellow, grey hair. Did you meet him?"
"Nope, never heard of Phillips."
"You went to the Harvard Business School and you don't know two of the most popular professors?! I don't get it. Did you attend Harvard or not?"
"Well, I guess I should be honest with you. I didn't actually go to Harvard. My roommate attended the Harvard Business School. He used to bring home all his notes and textbooks, and I read everything he brought home. So when he graduated, I figured I graduated, too."
The interviewer was not impressed. And our "graduate" didn't get the job. (Or if he did, it's one of those firms that's out of business now...)
Why isn't it enough just to read the notes to be considered a Harvard graduate?
Because you need to hear the lectures. The professors add so much information that the notes simply don't present a full view of the subject. If you want to get a full understanding of a text, what's the best way to find out? Ask the experts: "What's behind this? Please explain it."
Information in the written form is, by definition, secondary and limited in scope. That's why the Oral Torah is 50 times the size of the Written Torah! (In actuality, the Oral Torah is infinite. It contains the totality of Torah, which – as the word of the infinite God – is by its very definition infinite.)
Advantage of the Oral Torah
If the Oral Torah is such a great idea, then why isn't the Torah entirely oral? Because the Written Torah is necessary to provide the basics. If everything was by heart, then you'd have no reference point at all. There has to be a shell from which to extract the vast Torah teachings.
Rabbi Aryeh Kaplan explains in his "Handbook of Jewish Thought" (Moznaim 1979):
The Oral Torah was originally meant to be transmitted by word of mouth. It was transmitted from master to student in such a manner that if the student had any question, he would be able to ask, and thus avoid ambiguity. A written text, on the other hand, no matter how perfect, is always subject to misinterpretation.
Furthermore, the Oral Torah was meant to cover the infinitude of cases which would arise in the course of time. It could never have been written in its entirety. It is thus written (Ecclesiastes 12:12), "Of making many books there is no end." God therefore gave Moses a set of rules through which the Torah could be applied to every possible case.
If the entire Torah would have been given in writing, everyone would be able to interpret it as he desired. This would lead to division and discord among people who followed the Torah in different ways. The Oral Torah, on the other hand, would require a central authority to preserve it, thus assuring the unity of Israel...
Oral Teachings Help You Remember
Do you have an encyclopedia? When was the last time you used it? Most people haven't looked at their encyclopedia in ages. Usually, the only time you use an encyclopedia is when you need to look up something specific. Otherwise, it is just a reference work that sits on your bookshelf.
This was God's objective in devising the Oral Torah. Because Judaism is not a reference work made to sit on a shelf. Torah is meant to be lived and internalized. To do that, you need to know it backwards and forwards. That's why God gave us both a Written Torah and an Oral Torah. The basics are laid out in writing, but the rest of it must be learned orally, encouraging every Jew to constantly review and remember.
Furthermore, when it's oral, people must transmit it personally from teacher to student, from parent to child. That way, it's constantly on everyone's lips, being discussed and clarified.
The Talmud articulates this idea (Eruvin 54b):
Rebbe Eliezer learned: A person is obligated to teach his student each lesson four times. This is deduced by the following inference: Aaron – who learned from Moses who learned it from God – had to learn his lesson four times; how much more so an ordinary pupil who learns from an ordinary teacher.
Rebbe Akiva said: Where do we know that a teacher must continue to repeat the material until the student has mastered it? Because the Torah says (Deut. 31:19), "And you shall teach it to the children of Israel." And where do we know that it must be taught until the students know it fluently? Because the Torah says (ibid.), "Put it in their mouths." And where do we know that the teacher must also explain the reasons? Because the Torah says (Exodus 21:1), "Now these are the ordinances which you shall put before them
Because the Jews have had such a turbulent history, parts of the Oral Torah were written down because it was in danger of getting lost. Even still, the majority of the information remains oral until today.
God – in His infinite wisdom – devised the consummate system for transmitting Torah throughout the generations. It is not a written law, and it is not an oral law. It's both.