STEPHANUS ON THE BOOK "ON INTERPRETATION" [Aristotle page 16a 20, 27]

...of a premise, it is an expression; but as a part of a syllogism, it is a term. He discussed these things in the Categories only as simple vocal sounds signifying simple things, without being concerned whether it is a name, a verb, an expression, or a term, but only that it is a meaningful sound. Here, however, he discusses them as parts of premises and as predicates and subjects; whereas in the Prior Analytics, he discusses them as parts of a syllogism.

p. 16a 27 "By convention" means that none of the names exists by nature.
Someone might ask how Aristotle can say here that "none of the names exists by nature," when Plato appears to say in the Cratylus that names do exist by nature. One must understand, then, that "by nature" has two meanings, and "by convention" also has two. Something is said to be "by nature" if it is produced by nature itself, just as we say the eye, the nose, the ear, or the foot is a product of nature. On the other hand, "by nature" is also used for something that is suitably assigned, as when we say "horse" original: "hippos" because it "goes with its feet" original: "ienai tois posin" or "man" original: "anthrōpos" because he "turns his vision upward" original: "anō thēn ōpa"—that is, he is able to look upward with his eyes. Similarly, one might call "Archelaus" one who has a "ruling disposition," or "Basil" one who is "able to be a king."

Thus, "by nature" has two senses: either that which is generated by nature, or that which is suitably assigned based on the examples mentioned. The text here has a gap. Based on contemporary commentaries like Ammonius, Stephanus likely followed with: "Likewise, 'by convention' has two senses: either that which is suitably assigned—which is the same as the second sense of 'by nature'—" or that which is assigned simply and at random. f. 41v Now, Cratylus used to say names exist "by nature" according to the first meaning (biological production). Diodorus, however, said they were not "by nature" but "by convention," specifically according to the second meaning of convention: that they are assigned simply and at random. This is why he even called his own children by the names of grammatical conjunctions, naming them "Men" and "De." Diodorus Cronus was a philosopher who wanted to prove names are arbitrary; "Men" and "De" are Greek particles usually translated as "on the one hand" and "on the other hand."

It is clear that neither of them speaks entirely correctly. Socrates, acting as an arbiter in the dialogue, said that names are "by nature," not according to the first sense of "by nature" nor the second sense of "by convention" The text is corrupt here; the sense should be: "not according to the sense of being biological products, but in the sense of being fittingly assigned." which is the same as the first sense of "by convention." It is clear that it is impossible for names to be "by nature" (in the biological sense) because of homonymy (one name for many things), the changing of proper names, polyonymy (many names for one thing), different dialects, and those who are deaf from birth.

For if names existed by nature, proper names should not be changed; for example, Paris should not have been renamed Alexander, nor Pyrrhus renamed Neoptolemus, nor Aristocles renamed Plato—for long ago, Plato was named Aristocles. Plato was a nickname meaning "Broad," allegedly given by his wrestling coach. Furthermore, the same thing should not have many names, such as "dagger," "broadsword," and "blade," which all refer to one object. And why would people want there to be homonyms if names were set by nature? And dialects also show that names are not by nature; for we know that the same thing is named differently according to the specific character of various dialects. Another...