Pater filiis dicit iudicem aequum esse oportere, sive reus dives sit sive pauper.

Because filiis is the indirect object of dicit.

• pater = the father / a father
• filiis = to the sons / to his children
• dicit = says

So Pater filiis dicit means The father says to his sons.

For a learner, this is a very common use of the dative: the person to whom something is said, given, shown, etc.

Because Latin usually does not use a separate word meaning that after a verb of saying, thinking, knowing, and so on. Instead, it often uses an indirect statement construction.

Here the reported statement is put into the infinitive:

• direct: iudicem aequum esse oportet
• reported after dicit: iudicem aequum esse oportere

So instead of literally saying he says that..., Latin says something more like he says ... to be necessary.

This is one of the most important Latin constructions to get used to.

Oportere is the infinitive of oportet, an impersonal verb meaning it is proper, it is necessary, or more naturally in English, ought.

A very common Latin pattern is:

• aliquem + infinitive + oportet
• literally: it is necessary for someone to...
• more naturally: someone ought to...

So:

• iudicem aequum esse oportet = the judge ought to be fair

In this pattern, the person involved is often put in the accusative, which is why you get iudicem.

Then, because the whole statement is being reported after dicit, oportet becomes oportere:

• dicit iudicem aequum esse oportere
• he says that the judge ought to be fair

So iudicem is accusative because of the construction with oportet/oportere.

Because oportere needs to say what the judge ought to do or be.

Here the idea is not the judge ought to judge, but the judge ought to be fair. Latin expresses that with:

• iudicem aequum esse
• literally: the judge to be fair

So the structure is:

• iudicem = the judge
• aequum = fair
• esse = to be

Together they form the idea the judge to be fair, and that whole idea is governed by oportere.

Aequum agrees with iudicem.

Since iudicem is:

• masculine
• singular
• accusative

the adjective describing it must also be:

• masculine
• singular
• accusative

So:

• iudicem = judge (accusative singular)
• aequum = fair (accusative singular masculine, agreeing with iudicem)

This is a predicate adjective with esse: the judge to be fair.

A learner may wonder whether aequum is neuter here, but it is not. It is masculine accusative singular, matching iudicem.

Because reus belongs to a different clause.

• iudicem belongs with aequum esse oportere
• reus belongs with sit

So:

• iudicem aequum esse oportere = that the judge ought to be fair
• sive reus dives sit sive pauper = whether the defendant is rich or poor

In the sive ... sive ... clause, reus is the subject of the finite verb sit, so it is in the nominative.

That is why the sentence contains both:

• an accusative subject-like word: iudicem
• a nominative subject: reus

They are doing different jobs in different parts of the sentence.

Sive ... sive ... means whether ... or ....

So:

• sive reus dives sit sive pauper
• whether the defendant is rich or poor

It presents two alternatives and says that the main point is true in either case.

In this sentence, the idea is:

• the judge ought to be fair
• whether the defendant is rich
• or poor

You can also think of it as slightly like be he rich or poor in more formal English.

Because after sive ... sive ..., Latin often uses the subjunctive when the alternatives are presented in a general or indefinite way.

Here the sentence is not mainly making a factual statement about one particular defendant. It is expressing a principle:

• the judge should be fair,
• whether the defendant is rich or poor

Latin commonly uses the subjunctive in this kind of alternative clause, so sit is natural.

A rough way to feel the difference is:

• est would sound more straightforwardly factual
• sit suits the idea whether he be rich or poor

English usually does not show this distinction as clearly.

It is understood from the first half.

Latin often omits a repeated word when the meaning is clear. So:

• sive reus dives sit sive pauper means
• sive reus dives sit sive reus pauper sit

But Latin does not need to repeat everything.

This kind of omission is very common and perfectly normal.

Yes. Pauper is an adjective meaning poor, just as dives means rich.

Both dives and pauper describe reus:

• reus dives = a rich defendant
• reus pauper = a poor defendant

They are in the nominative singular because they agree with reus, the subject of sit.

A learner may notice that dives and pauper do not look like first/second-declension adjectives such as bonus, bona, bonum. That is because they belong to different adjective patterns, but they still agree with the noun they describe.

Because Latin has no articles.

Latin does not have separate words for the, a, or an. So a noun like pater can mean:

• a father
• the father
• sometimes his father

depending on context.

The same is true for:

• filiis = to the sons / to his sons
• iudicem = the judge / a judge
• reus = the defendant / a defendant

English has to choose an article when translating, but Latin leaves that to context.