[See Latin Line by Line for an introduction to this concept.]
The Story So Far:
In the first 3 chapters of Book 1, Livy has discussed the pre-history of Rome. At the end of chapter 3, the city of Alba Longa has been founded. The last king, Aventinus, has died, survived by his two sons Numitor and Amulius. Though Numitor was the eldest and thus had the legal right to rule, Amulius forcibly expelled him, killed his sons, and appointed his niece a Vestal Virgin to deprive her of the possibility of bearing more children who could claim the throne. Amulius also raped her. In doing so, however, he set in motion his own undoing. Our selection today begins the story of Remus and Romulus, legendary founders of Rome.
Step 1: The Text as a Whole (quickly read, look up vocab)
Sed debebatur, ut opinor, fatis tantae origo urbis maximique secundum deorum opes imperii principium. Vi compressa Vestalis cum geminum partum edidisset, seu ita rata seu quia deus auctor culpae honestior erat, Martem incertae stirpis patrem nuncupat. Sed nec di nec homines aut ipsam aut stirpem a crudelitate regia vindicant: sacerdos vincta in custodiam datur, pueros in profluentem aquam mitti iubet.
Step 2: Sentence work (read for thorough comprehension)
Sed debebatur, ut opinor, fatis tantae origo urbis maximique secundum deorum opes imperii principium.
Sentence kernel: debebatur fatis origo -que principium
Let’s start with the noun phrases that serve as the subjects. Each subject gets a genitive modifier: tantae origo urbis (origin of such a great city) … maximique imperii principium (beginning of the greatest empire). Probably stylistically to balance the “fatis” by the first subject, the second subject gets a further modifying prepositional phrase: secundum deorum opes principium (second to the might of the gods). [Note: ops is often used in the plural (opes) where English prefers the singular; omnibus operibus –> with all our mights –> with all our might.]
Now for the verb and its modifier. “Debebatur” here in the passive means “is due to.” The obvious question is due to whom or what? The answer comes in the dative: “fatis” (to the Fates).
Finally, sentence-level connectors and other odd bits. “Sed” (but) introduces the sentence, implying that the narrative of Amulius’ treacherous rise is about to be reversed. “ut opinor” (“as I suppose” or “in my opinion”) is Livy’s narrator commentary, also called a “disjunct” in some grammars.
All together with some smoothing: But I suspect that the origin of such a great city and the beginning of the greatest empire, second in might only to the gods, is due to the Fates.
Vi compressa Vestalis cum geminum partum edidisset, seu ita rata seu quia deus auctor culpae honestior erat, Martem incertae stirpis patrem nuncupat.
This sentence is more complex, but the kernel is easy enough to do in one step: Martem incertae stirpis patrem nuncupat (she named Mars as the father of the uncertain progeny –> as the father of the children of uncertain lineage). Note how the two accusatives flank the modifying genitive phrase. That’s a common and very good stylistic decision.
Now the kernel of the cum clause: “Vestalis cum geminum partum edidisset” (when the Vestal had issued forth a twin birth). Vestalis here is a nominative and the subject of the cum clause. When the subject of a cum clause is also the subject of the main clause coming later in the sentence, the subject sometimes moves to this fronted position. Since we’re here, let’s add the phrase modifying the subject: “vi compressa Vestalis” (the Vestal having been “pressed” by force –> a euphemism for rape).
This cum clause is further modified by a pair of seu (either/or) clauses: “seu ita rata” (either her believing [it to be] so) // “seu quia deus auctor culpae honestior erat” (or because a god was a more noble author of the crime).
All together: “After the Vestal virgin had been raped, she gave birth to twins. Either because she thought it was true or because a god would be a more noble perpetrator of the crime, she named Mars as the father of the children of uncertain lineage.” Note that by splitting it into two sentences, I lost the time connection between the pluperfect verb (edidisset) and the perfect (nuncupat). However, since I don’t think Livy’s point is to stress a time lapse between the birth and her claiming divine parentage for the children, I judged it to be an acceptable loss.
Sed nec di nec homines aut ipsam aut stirpem a crudelitate regia vindicant: sacerdos vincta in custodiam datur, pueros in profluentem aquam mitti iubet.
There are actually three independent clauses here. The first has two subjects connected by nec-nec (neither-nor), as well as two objects connected by aut-aut (either-or): “Sed nec di nec homines aut ipsam aut stirpem a crudelitate regia vindicant” (But neither gods nor people delivered either her or the progeny from royal cruelty.”
The second clause uses the idiom “in custodiam datur” (is delivered into keeping) to mean “was imprisoned.” “sacerdos vincta in custodiam datur,” (the priestess was cast chained into prison).
The third clause uses a verb of command. These verbs are completed by an infinitive and (usually) an accusative. Often the accusative specifies the person being ordered and an active infinitive expresses the content of the command. Here, though, a passive infinitive is used, so the accusative expresses on whom the order is to be carried out. The person being ordered is left undefined. “pueros in profluentem aquam mitti iubet” (He [the king] ordered the boys to be thrown into running water –> into the river).
All together: “But neither gods nor people delivered either her or the progeny from royal cruelty. The priestess was sent chained into prison; the boys he ordered cast into the river.”
So if there were three independent clauses, why does the text’s punctuation divide the sentence into two unequal halves? Latin punctuation is as much about meaning and narration as about grammar. The first half of the sentence, up to the colon, makes a summary statement. The second half shows how that statement is worked out in two different ways. So the sentence is balanced between general and specific, or between foreshadowing and fulfillment. That’s style. I tried to preserve some of that in English by making the two halves two equal sentences, and then equally subdividing the second sentence into two equal clauses. Successful? You decide.