The speaker addresses someone absent or dead, a thing, a place or an idea, as if they could hear.
In the Aeneid
O thrice and four times happy those who were fated to die before their fathers' eyes, beneath the high walls of Troy!
Aeneas addresses the dead with “O thrice and four times happy,” as if the dead of Troy could hear him in the middle of the storm. The cry aloud turns his fear into envy of those dead.
Book I: The Storm and Carthage, Aeneas
It is war, O hospitable land, that you bring: horses are armed for war, these herds threaten war. But these same quadrupeds are used to draw the chariot and to bear, in harmony, the bit under the yoke: there is hope of peace.
Book III: The Wandering, Anchises
Ah! I was the cause of your death! I swear by the stars, by the gods above and by whatever faith there is under the deep earth: against my will, queen, I left your shore
Book VI: The Descent to the Underworld, Aeneas
Hail, land owed to me by the fates; and you, he said, faithful Penates of Troy, hail! Here is the home, this is the homeland.
Book VII: The Arrival in Latium, Aeneas
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