Avus dicit virtutem sine patientia et sine bona voluntate firmam esse non posse.

Because after dicit, Latin uses indirect statement very often.

In this construction:

• the subject of the embedded statement goes into the accusative
• the verb of the embedded statement goes into the infinitive

So instead of using a clause like that virtue ... cannot be firm, Latin says, more literally:

• avus dicit = grandfather says
• virtutem = virtue, as the accusative subject of the indirect statement
• esse non posse = not to be able to be

So virtutem is not the direct object of dicit in the usual English sense; it is the subject of the infinitive phrase inside the indirect statement.

Dicit introduces what Latin grammar calls an accusative-and-infinitive construction.

The pattern is:

• main verb of saying/thinking/perceiving
• then accusative subject
• then infinitive verb

Here:

• Avus dicit = the grandfather says
• virtutem ... firmam esse non posse = that virtue cannot be firm

This is one of the most important Latin constructions to learn, because English often uses that, while Latin often uses accusative + infinitive instead.

Because they are governed by the preposition sine, which takes the ablative case.

So:

• sine patientia = without patience
• sine bona voluntate = without good will

Whenever you see sine, you should expect an ablative noun after it.

Because voluntate is ablative singular after sine, and the adjective must agree with the noun it modifies.

So:

• noun: voluntate = ablative singular
• adjective: bona = ablative singular feminine, agreeing with voluntate

Latin adjectives must match their nouns in:

• gender
• number
• case

That is why you get bona voluntate, not bonam voluntatem.

Because firmam is a predicate adjective agreeing with virtutem.

In the indirect statement, virtutem is accusative feminine singular, so the adjective describing it must match:

• virtutem = accusative feminine singular
• firmam = accusative feminine singular

Even though English says virtue cannot be firm, Latin makes both the noun and its predicate adjective accusative inside indirect statement:

• virtutem firmam esse = virtue to be firm

Because posse already means to be able, and it is followed by another infinitive that tells you able to do what.

So here:

• posse = to be able
• esse = to be

Together:

• esse posse = to be able to be

With non:

• esse non posse = not to be able to be

That may feel awkward in English, but it is perfectly normal in Latin.

Because non is negating posse, not esse.

The idea is:

• not to be able
• to be firm

So the structure is:

• firmam esse = to be firm
• non posse = not to be able

Put together:

• firmam esse non posse = cannot be firm

If non were aimed at esse, the sense would be different. Here the point is not that virtue is not firm, but that it cannot be firm under those conditions.

Latin can repeat a preposition for clarity or emphasis.

So:

• sine patientia et sine bona voluntate means without patience and without good will

Repeating sine can make the sentence feel more deliberate, as if each missing quality is being separately emphasized.

Latin could also sometimes say:

• sine patientia et bona voluntate

But the repeated preposition is entirely normal and often stylistically clearer.

Avus is the subject of the main verb dicit.

So:

• avus = grandfather
• dicit = says

Everything after that belongs to what he says.

This means the sentence has:

• a main clause: Avus dicit
• an indirect statement: virtutem ... firmam esse non posse

Yes. In this sentence, firmam esse functions together as the verbal idea inside the indirect statement.

More specifically:

• esse is the infinitive verb
• firmam is the predicate adjective attached to it

So Latin expresses to be firm as:

• firmam esse

Then that whole idea is governed by posse:

• firmam esse posse = to be able to be firm
• firmam esse non posse = not to be able to be firm

Because Latin word order is much freer than English word order.

Latin often puts important verbal material near the end, especially in more formal or literary style. Here the final non posse gives a strong ending to the whole thought.

English relies heavily on word order for grammar, but Latin relies much more on:

• case endings
• verb forms
• agreement

So even if the order feels unusual to an English speaker, the grammar is still clear.

Sometimes Latin can use quod + a finite verb, especially in later Latin or in certain styles, but after verbs like dicit, the accusative-and-infinitive is the standard classical construction.

So in classical Latin, this sentence is exactly what you would expect:

• dicit
• virtutem
• firmam esse non posse

That is one reason this sentence is a very useful example for learners: it shows a common and fundamental Latin pattern.

A learner might want to identify the forms like this:

• avus from avus, -i = grandfather
• dicit from dico, dicere, dixi, dictum = say
• virtutem from virtus, virtutis = virtue
• patientia from patientia, -ae = patience, endurance
• voluntate from voluntas, voluntatis = will, goodwill
• firmam from firmus, -a, -um = firm, strong, steady
• esse from sum, esse = to be
• posse from possum, posse = to be able
• non = not
• sine = without

Seeing the dictionary forms often helps explain why the case endings look the way they do in the sentence.