Let’s first see what’s traditionally said about the Oral Torah, that part of the Tradition that wasn’t set in writing which expands upon, explains, and illustrates the written Torah. And then we’ll see all that Ramchal adds to it.
We’re taught that “All the mitzvot given to Moses at Mount Sinai were presented along with their interpretation…. Moses wrote down the entire Torah before his death, in his own hand. He gave a Torah scroll to each tribe and placed another scroll by the Ark for a witness…. He did not write down … the interpretation of the Torah, but he gave orders about it to the elders, to Joshua, and to all the rest of Israel …. That is why it is called ‘The Oral Torah'” (Rambam’s Introduction to Mishne Torah, paragraphs 1-3). And so we see that both the Torah text itself and the Oral Torah (which came to be written down later on as the Mishna, Talmud, Midrash, etc.) were both revealed at the same time.
There are in fact many indications of the existence of an Oral Tradition in the text of the Torah itself (see R’ Yehudah Halevy’s Kuzari 3:35). We’re told, for example, that “This month will mark the beginning of the months for you” (Exodus 12:2), but which month was this verse talking about? Was it the Egyptian one (don’t forget, our people had just come out of Egypt), the Chaldean one (which was a major civilization at the time, and the one out of which Abraham, our forefather, had come), was it a Lunar month or Solar month? So we see that there had to been an answer to that which wasn’t put in words.
What does the Torah mean when it says that animals could only be eaten after being “slaughtered” (see Deuteronomy 12:21)? What process is involved in that? Nothing is specified. Besides, we’re told there to “slaughter from your herd and your flock … as I have commanded you”, when no commandment of the sort is stated in writing, so it had to have been transmitted orally.
We’re told “It is a mitzvah for all time throughout the ages, in all your settlements: you must not eat any fat or any blood” (Leviticus 3:17). But there are two distinctly different sorts of fats on an animal: the soft kind and the hard kind (the first of which is permissible while the second, known as suet, is not). How would we know which was permissible if we weren’t told outright?
The Torah says, “Let no man leave ‘his place’ on the seventh day” (Exodus 16:29). What “place” is it referring to? — a person’s home, perhaps, but which one if he owned more than one; is it referring to his neighborhood, his city, or to something else? We would need an answer for that which the Torah doesn’t provide. Besides, it’s written elsewhere that “at every New Moon and on every Shabbat all20mankind will come to bow down before Me, said G-d” (Isaiah 66:23) which clearly indicates that the people were in fact to leave their “place” on the Shabbat! There had to have been an unwritten rule about leaving and not leaving one’s “place”.
What does the Torah mean when it forbids “work” on Shabbat (see Exodus 20:10)? What sort of work? What’s involved in a circumcision, as depicted in Genesis 17:10-14? What comprises the Tefillin we’re commanded to don in Exodus 13:16? What are Tzitzit comprised of (see Numbers 15:38-39)?
Even more fundamentally the point should be made that the Torah-scroll is written without vowels or punctuation, making it impossible to read and understand without a tradition.
So it’s clear that a lot was left unwritten … but not unsaid.
Rabbi Yaakov Feldman has translated and commented upon “The Gates of Repentance”, “The Path of the Just”, and “The Duties of the Heart” (Jason Aronson Publishers). His works are available in bookstores and in various locations on the Web.