Jacob Neusner, Invitation to Midrash: The Workings of Rabbinic Bible Interpretation (Atlanta: Scholars, 1998) 49.
...the Talmud of the land of Israel, subordinate as it is to the Mishnah, regards the Mishnah as subordinate to, and contingent upon, Scripture.
The Talmud is an interpretation of the Mishnah, a Jewish law code/educational manual that was completed in 200 C.E. (except for the parts that were added later). The Mishnah doesn't always support its statements with Scripture, but the Talmud tries to connect them with biblical verses, Neusner argues. In the same way that the authors and compilers of the Talmud viewed themselves as subordinate to the Mishnah, they believed that the Mishnah was subordinate to the Scriptures.
How can this be, if Pirke Avot (250 C.E.) declared that the Mishnah was given at Sinai? Wouldn't that make it authoritative, period?
During my time at Hebrew Union College, I've heard that Jewish religion has a hierarchy of authority. The later Amoraic rabbis are deemed less authoritative than the earlier Tannaitic rabbis. The rabbis are subordinate to the Scriptures. And there's a hierarchy of authority within the Scriptures, as the Torah outranks the Prophets and the Writings.
I wonder how something can be "more" or "less" authoritative. This may be the fundamentalist part of me speaking, but either something is totally true and authoritative, or we can't be certain about what is true and authoritative, right?
At the same time, even fundamentalism has its hierarchy, for it says that we should interpret the obscure passages of Scripture in light of the clearer passages. Is that how the rabbis are treating the Jewish tradition? Sure, we can somewhat trust the Prophets, the Writings, and the Rabbis, they may be thinking, but we can only absolutely trust the written Torah. So we go with the less authoritative traditions, unless there's a conflict with more authoritative traditions, and ultimately the written Torah.
One should remember, though, that rabbinic Judaism isn't necessarily afraid of being wrong. Because God has given the rabbis the authority to make decisions, what they say goes, even if a voice from heaven contradicts them (according to the Babylonian Talmud). But their decisions are not arbitrary, for they want to be faithful to the tradition as they seek God's will. They desire some degree of certainty, and that's why they try to tie the Mishnah with Scripture, or uphold a hierarchy of authority (i.e., such-and-such is fairly reliable, but this is more reliable).