Here's a sugya I took a peek at after discussing it briefly with a friend. This is my half-baked first impression of what's going on...
The gemara in Sotah 6A deduces from the Mishna that, with regard to evidence, Eidim trump Sotah. On one hand, this seems obvious. The sources in Chazal give us much reason to doubt the reliability of the Sotah test:
- If she was otherwise meritorious, the effect of the test may be delayed(our gemara)
- If there was a witness, the test may not work(our gemara)
- If her husband sinned similarly then the test may not work(Rambam Hilkhot Sota 2:8)
- If Israel’s spiritual state is poor then the test may not work(Rambam 3:17-19)
On the other hand, these are all special cases and the bottom line is that the Torah relates to the Bdikat Sotah as proof.
Rav Sheshet vs. Rav Yosef
Getting back to our gemara, there’s a debate as to why Eidim who come after the Bdikat Sotah are believed over the Bdikah.
- Rav Sheshet- because the very existence of the witnesses keeps the Bdikat Sotah from working
- Rav Yosef- Because the wife’s zchut may delay the action of the Bdikah Sotah
The gemara connects their debate to a potential Machloket Tanaim about how fast the Bdikat Sotah works in the case of זכות תולה לה. The question is whether it’s effects are visible immediately, though it may take a long time for death to ensue, or whether it’s effect may occur suddenly after a long time.
Miraculous Sign vs. Imperfect Proof
So what is the fundamental debate here? I’d like to suggest that it has to do with our initial question, of how good a proof we consider the Bdikat Sotah to be.
The Torah gave us this alternative form of judgement in the case of the Sotah because of the value of the family and the need to resolve the conflict between spouses. But how good is this proof? Is Sotah a better proof than Eidim because it’s a miraculous sign? Or is it a worse proof than Eidim because of its unreliability, even though it should still be enough to satisfy a suspicious husband? Which of these aspects of Sotah is dominant?
Rav Sheshet- at a basic level, it's a better proof than Eidim due to the divine nature of the sign. But if there exist Eidim then there is no bdikat Sotah.
Rav Yosef- due to the unreliability, it's a worse proof than Eidim, so that if witnesses do appear later then we prefer their testimony to miraculous signs.