פירוש על סוטה 43:16

They issue halachic rulings from their mishnayot -- it says "they erode the world" with mistaken teaching, since they do not know the reasons of the mishna, which leads them to compare it to a thing to which it is not similar. And further, there are many mishnayot which are said like Ploni, and Ploni is an individual voice and the halacha is not established from such. And further, they do not know about the disagreements (machlokot) of the first/former tannaim, who the halacha is like -- and therefore they teach mistakenly.

And [the Talmud] further [recounts] ibid [Sotah 22a]: '[If] he has read [i.e., studied Scripture] and studied the Oral Law, yet did not apprentice himself to Torah scholars - Rabbi Eliezer says: this one is a commoner; Rabbi Samuel son of Nachmeni says: this one is an ignoramus; Rabbi Yanai says: this one is a Samaritan; Rav Acha son of Jacob says: this one is a magus. Rav Nachman son of Isaac said: The opinion of Rav Acha son of Jacob seems most plausible, as people say: A magus chants without knowing what he's chanting; a tanna teaches without knowing what he's teaching.' And the explanation of this [Talmudic passage] is that, when he studied the Law [lit: Mishna] but did not apprentice himself to a Torah scholar to clarify the reasons for the Law - for it is a clear mind [that one has] when one has arrived at [lit: stood upon] the reasons for the Law - [such a one who has failed to do this clarification by appreticing to a scholar] is called a commoner [am haaretz] inasmuch as he did not acquire an intellect. And Rabbi Samuel added [to this] to say that he is called an ignoramus [bur], for a filed that does not produce is called a fallow field [sadeh bur], just as the Targum of