| Quote #1
These words are spoken by Juno near the beginning of Book 1, when she sees Aeneas and company happily sailing toward Italy. The irony is that, to each and every one of these questions, the answer is "Yes." Juno will have to give up what she began (destroying all the Trojans), and in this sense she is defeated. The king (Aeneas) of the Teucrians (Trojans) will make it to Italy and found a new city. Why? Because it is fated. That said, the poem would be pretty boring if Juno just sat down and accepted all that, wouldn't it? The thing is, the Romans didn't see "Fate" and "Free Will" as completely opposite concepts; even if it was fated that something would happen, there still was a lot of wiggle room over how it would happen. Juno decides to make the most of that wiggle room, and make the Trojans' life a living underworld until they can finally found their city.
| Quote #2
Then, even then, Cassandra's lips unsealed
Along with Laocoön, who throws a spear at the wooden horse and is subsequently killed by snakes, the figure of Cassandra tantalizes the reader with alternate possibilities for how the fall of Troy might have played out. Assuming that Cassandra hadn't been condemned to be disbelieved, do you think she would have had any better luck at convincing the Trojans of their danger? To help you think about this question, look at Virgil's description of crowd psychology a few lines earlier (2.314-329) as the Trojans are hauling the horse into the city.
| Quote #3
Venus speaks these words to stop Aeneas from killing Helen, whom he blames for bringing destruction on the Trojans. On the surface, Venus's words look like a straight-up statement of how we aren't to blame for our fate – and hence it makes no sense for Aeneas to take his anger out on Helen. (As can be seen in the other quotes in this section, the Aeneid usually portrays the interaction between Fate and Free Will as a bit more nuanced than that.) On a deeper level, though, it is good to bear in mind something that every reader of the Aeneid would have known from Homer's Iliad: that Venus herself (a.k.a. Aphrodite) was the one who made Helen run off with Paris. In a sense, what Venus might really be saying is, "Hey, I'm the one who made her do it, so leave her out of this."