…texts, and oral texts in particular, become defective only if they are not carefully preserved, if they are not faithfully and reliably transmitted. In this case, we would have to assume that during the Talmudic period, certain texts (those that required redactional changes) composed by some of the great sages were transmitted haphazardly, in an incomplete and defective state. Some texts eventually may even have disappeared altogether: neglecting to preserve texts properly leads not only to defectiveness, but also to disappearance,

David Weiss Halivni, Midrash, Mishnah, and Gemara: The Jewish Predilection for Justified Law (Cambridge, MA & London, UK: Harvard University Press, 1986), 2.