Jacob Neusner, The Midrash: An Introduction (Northvale: Jason Aronson, 1990) 106.
Neusner sums up the essence of Sifre Numbers (third century C.E.) as follows:
1. Reason unaided by Scripture produces uncertain propositions.
2. Reason operating within the limits of Scripture produces truth.
Does reason ever operate within the limits of Scripture? Interpreters throughout history have brought their own cultural contexts into their interpretation. When Philo (first century C.E.) interprets the Torah, for example, he seems to be reading Greek philosophy into the text (eisegesis), rather than getting it out of it (exegesis). But he undoubtedly thinks he's doing exegesis. People have tried to reconcile the Bible with the science or philosophies--the "knowledge"--of their day.
I wonder if historical-criticism does this, since it doesn't proceed on the notion that the Bible is truth, and it tries to read the Bible in light of its own context, not today's. Yet, people have claimed to identify ideological bias in practitioners of the historical-critical method: Wellhausen's method has been labeled anti-Jewish, for example.
Suppose we only operated within the limits of Scripture? Would that require us to see the world as flat, with four corners and a vault over it, and the sun roaming through the heavens? Many claim this is the cosmology of the Bible. Others maintain, however, that the Bible is being figurative when it uses such language.
Do the "limits of Scripture" guarantee certainty? Perhaps it narrows things down a bit, since we can now find truth in one book. But what if that one book speaks with different voices? And why are there so many denominations?
Of course, the rabbis didn't just operate within the limits of Scripture, for they had an interpretive tradition. But Neusner's point is that Sifre Numbers tries to ground the Mishnah's rules in Scripture, as well as looks to Scripture to resolve disputes.