H.L. Strack and Gunter Stemberger, Introduction to the Talmud and Midrash: Second Edition, trans. and ed. Markus Bockmuehl (Minneapolis: Fortress, 1996) 138.
Given today's knowledge, it is no longer possible unequivocally to determine whether M [(the Mishnah)] was originally conceived as a collection, a teaching manual or a law code. Indeed this alternative probably arises only for modern readers; what is more, it fails to account sufficiently for the utopianism of M, its idealized order of the perfect harmony of heaven and earth, and the underlying philosophy. In principle, the ancient tradition is of course regarded as law which must be transmitted in teaching--and thus the three concepts almost coincide. And a certain development cannot be excluded. The summary of the halakhah in Rabbi [Judah ha-Nasi]'s school, with its endeavor to include a great variety of rabbinical opinions, will at the same time have been a political move intended to unite Judaism under the direction of the patriarchate: although primarily the basis of teaching in schools, it was also the foundation for the judgments in Rabbi's court. Rabbi's exceptional authority then led to the work being regarded as a code of binding law for all of rabbinic Judaism, like the Bible the cornerstone and basis of new developments by interpretation (cf. Epstein, ITM: the attitude to M changes from about the third Amoraic generation; where necessary, it now came to be interpreted very unnaturally or subjected to textual correction, but it was no longer contradicted with baraitot).
This paragraph is a good summary of Strack and Stemberger's discussion of the Mishnah. What was the Mishnah originally: a law code, a teaching manual, or a collection? Some say it's too messy to be a law code, too vague to be a teaching manual, and too incomplete to be a collection. Yet, it is trying to tell Jews what to do, and it presents the views of various teachers.
I've been reading the Mishnah for my daily quiet time, and I've wondered how the Mishnah could be a law code if it doesn't resolve every single dispute it records. Strack and Stemberger suggest that "the redactor would transmit a decision undecided, and insert his own opinion elsewhere" (137). So I guess arriving at halakhic decisions can sometimes be a game of "Where's Waldo?" But there's a degree of logic to that. The Mishnah is about what Jews are supposed to do, but there's also a rabbinic emphasis on "study, study, study." If everything were laid out neatly, would there be a need to study as much?
There's a parallel with how many Christians treat the Bible. I don't see the Bible as similar to OSHA regulations. Rather, reading the Bible is encountering a variety of voices from different times and places. If I want to learn about, say, compassion, I don't turn to a single part of the book, a compassion section, but I look at a variety of places where the topic comes up. And there are different shades in the Bible's presentation of compassion. The Bible isn't exactly the neatest book, yet it is a teaching manual and tells people what to do. It requires study, study, study. It's not about following a bunch of empty rules, but Bible study is seeking the mind of God, getting to know him and following the order he prescribes. So I'm not surprised that the Mishnah is the same way.