The final paragraph of this answer:
We do have the tools to derive from the Torah what those Halachos are (Moshe Rabeinu taught them to us), but these rules are very general in nature and therefore we get two opinions on how to learn a given Passuk.
got me thinking: why are there always two competing opinions (among Tannaim and Amoraim)? There are (almost?) never more opinions, and whenever there seem to be, the Gemara seems intent on aligning the third (and forth, fifth, etc.) opinion with one of the first two being discussed.