| Quote #16
[Virgil]: "I only ask you this: refrain from talking.
Here, one’s speech gives away his nationality. Virgil can tell by the language of Ulysses and Diomedes that they are Greek. However, he makes an assumption about them based on their language, supposing that they hold a grudge against the Trojans (and hence their descendants, the Italians) for their bitter enmity in the Trojan War, and thus forbids Dante from speaking to them. Language therefore becomes grounds for politics and racism.
| Quote #17
I still was bent, attentive, over him [Guido da Montefeltro],
Contrary to its role in the previous canto, language here becomes a tool for solidarity and unification under the same nation. Whereas Dante is not allowed to speak to Ulysses because he is Greek, here Virgil urges him to speak to Montefeltro because they use the same language. Thus, language can form a basis of nationalism.
| Quote #18
Who, even with untrammeled words and many
In witnessing the horrendous pain of the Sowers of Schism, Dante laments the inability of words to do justice to their suffering. There is a suggestion here that words simply do not have the capacity to capture such agony: "untrammeled," "tongue[s]…fall[ing] short," and "shallowness of…our speech" convey the message that physical and moral pain sometimes penetrate to a deeper depth than language can reach, and that at that point language becomes ineffective.