Multi cives arbitrantur bonam rem publicam sine iustitia servari non posse.

Because this sentence uses indirect statement after arbitrantur (they think / they believe).

In Latin, after verbs of thinking, saying, knowing, perceiving, and so on, English often uses that-clauses, but Latin usually uses:

• accusative subject
  • infinitive

So in:

Multi cives arbitrantur bonam rem publicam sine iustitia servari non posse

the part after arbitrantur is an indirect statement:

• bonam rem publicam = the subject of the indirect statement, so it goes into the accusative
• servari non posse = the infinitive part

If this were an ordinary main clause, you would expect bona res publica. But inside indirect statement, it becomes bonam rem publicam.

Arbitrantur is the 3rd person plural present indicative of arbitror, arbitrari, arbitratus sum.

It means:

• they think
• they judge
• they consider

A very important point: arbitror is a deponent verb. That means it has passive forms but an active meaning.

So although arbitrantur looks passive, it actually means they think, not they are thought.

Because arbitror is a deponent verb.

Deponent verbs are a special group in Latin:

• they use passive-looking forms
• but they have active meanings

So:

• arbitror = I think
• arbitraris = you think
• arbitrantur = they think

This is something English speakers often have to get used to, because English has nothing quite like it.

We know this from both form and structure.

• Multi cives is nominative plural: many citizens
• arbitrantur is 3rd person plural: they think

So multi cives matches arbitrantur as the main subject.

Then, after arbitrantur, Latin normally uses indirect statement. That means the next noun phrase functioning as the subject of the thought will be in the accusative, which is exactly what we get with bonam rem publicam.

So the structure is:

• Multi cives = main subject
• arbitrantur = main verb
• bonam rem publicam sine iustitia servari non posse = what they think

This is the infinitive part of the indirect statement.

Break it down:

• servari = to be preserved / to be maintained
  (present passive infinitive of servo)
• non posse = not to be able

Together:

• servari non posse = not to be able to be preserved
• more natural English: cannot be preserved

So Latin expresses the idea literally as a good state not to be able to be preserved without justice.

Because the meaning is to be preserved, not to preserve.

• servare = active infinitive = to preserve
• servari = passive infinitive = to be preserved

In this sentence, the good state is receiving the action. It is the thing being preserved. So Latin needs the passive infinitive:

• bonam rem publicam ... servari = that a good state is preserved / can be preserved

But since the sentence says it cannot be preserved, we get:

• bonam rem publicam ... servari non posse

Because the idea is cannot be preserved, not can fail to be preserved.

Latin places non before the word it most directly negates. Here it negates posse:

• non posse = not to be able

So:

• servari non posse = not to be able to be preserved
• natural English: cannot be preserved

If you changed the negation, the meaning could shift. Latin word order is flexible, but here the standard idea is simply cannot be preserved.

Because sine is a preposition that takes the ablative.

So:

• sine = without
• iustitia = ablative singular of iustitia, justice

Together:

• sine iustitia = without justice

This is just a standard prepositional rule you have to learn with the preposition.

Res publica literally means public thing or public affair, but in normal usage it means something like:

• the state
• the commonwealth
• the republic

In dictionaries you often see the nominative form:

• res publica

But here the phrase is in the accusative singular, so both words change:

• res → rem
• publica → publicam

So:

• res publica = nominative
• rem publicam = accusative

And because bonam modifies it too, we get:

• bonam rem publicam = a good state / a good republic

Latin word order is much freer than English word order.

Here:

• bonam modifies rem publicam
• publicam also modifies rem

Even though English usually keeps modifiers tightly together, Latin can separate related words more easily because the endings show the relationships.

In bonam rem publicam, all three words are:

• feminine
• singular
• accusative

So the grammar makes the connection clear.

Latin authors often vary word order for emphasis, rhythm, or style. In this sentence, the phrase still hangs together clearly because of the matching endings.

By itself, cives could be either nominative plural or accusative plural. The form is the same.

So how do we know it is nominative here?

Because of the sentence structure:

• multi cives fits naturally as the subject of arbitrantur
• arbitrantur needs a plural subject
• after arbitrantur, Latin normally uses an indirect statement, and that indirect statement already has its own accusative subject: bonam rem publicam

So context tells us that cives must be nominative here.

This is very common in Latin: sometimes the form alone is ambiguous, but the syntax makes the function clear.

Because Latin usually does not use a that-clause after verbs like think, say, know, hear, and so on.

Instead, it prefers indirect statement:

• accusative subject
  • infinitive

So English says:

• Many citizens think that a good state cannot be preserved without justice

But Latin says, more literally:

• Many citizens think a good state without justice not to be able to be preserved

That sounds strange in English, but it is completely normal in Latin.

Here the infinitives are present infinitives:

• servari = present passive infinitive
• posse = present infinitive

In indirect statement, the tense of the infinitive is relative to the main verb, not absolute in the same way as in English.

The present infinitive usually shows action happening at the same time as the main verb.

So the sense is:

• Many citizens think that a good state cannot be preserved without justice

That is, at the time they think this, they consider it generally true.

Yes. Latin has no articles.

So bonam rem publicam could, depending on context, be translated as:

• a good republic
• the good republic
• a good state
• the good state

English has to choose a or the, but Latin leaves that to the context.

In a general moral or political statement like this, English often uses a good state or a good republic.

A helpful way to see it is:

• Multi cives = subject
• arbitrantur = main verb
• bonam rem publicam ... servari non posse = indirect statement

And inside the indirect statement:

• bonam rem publicam = accusative subject
• sine iustitia = prepositional phrase
• servari non posse = infinitive phrase

So the whole sentence is built like this:

Many citizens + think + [that] a good state cannot be preserved without justice.

That is the key structure to recognize.