Nemo dubitat quin argentarius pactum signare debeat, antequam pecuniam det.

After a negative expression of doubt such as nemo dubitat (no one doubts) or non dubito (I do not doubt), Latin commonly uses quin to introduce the content clause.

So:

• Nemo dubitat quin ... = No one doubts that ...

A very literal sense of quin here is something like that not / but that, but in normal English you should usually just understand it as that after a negative main clause.

This is a standard Latin pattern:

• non dubito quin veniat = I do not doubt that he is coming / will come

Debeat is subjunctive because it is inside a quin clause after a negative expression of doubt.

That is one of the regular constructions in Latin:

• negative main idea of doubting
• followed by quin
• followed by a verb in the subjunctive

So in this sentence:

• Nemo dubitat quin argentarius pactum signare debeat

the clause beginning with quin is grammatically dependent on nemo dubitat, and that is why debeat is subjunctive rather than indicative.

Because with verbs of doubting, Latin often prefers a special construction.

A rough guide is:

• dubitare in a negative expression often takes quin + subjunctive
• some other verbs of saying, thinking, perceiving, etc. often take accusative + infinitive
• quod can introduce factual clauses in some contexts, but it is not the normal pattern here

So a learner should recognize non dubito quin... and nemo dubitat quin... as a set phrase/pattern.

Argentarius is the subject of debeat.

Inside the quin clause, the structure is:

• argentarius = subject
• pactum = direct object
• signare = infinitive dependent on debeat
• debeat = main verb of that subordinate clause

So the sense is that the banker/moneylender ought to sign the agreement.

Nemo means no one or nobody. Grammatically, it is singular, so it takes a singular verb:

• nemo dubitat = no one doubts

Even though it refers to people in general, Latin treats it as singular, just as English usually does with no one doubts, not no one doubt.

This is a straightforward verb + infinitive construction.

• debeat = ought / should
• signare = to sign
• pactum = direct object of signare

So:

• signare debeat = ought to sign
• pactum signare debeat = ought to sign the agreement

This is different from an accusative-and-infinitive construction. Here, pactum is simply the object of signare, not the subject of an infinitive.

After antequam (before), Latin can use either the indicative or the subjunctive, depending on nuance.

Here det is subjunctive because the action in the before clause is viewed as something still anticipated or pending relative to the obligation in the main clause:

• he should sign the agreement before he gives the money

The giving of the money is not being presented as a simple fact; it is an expected future step. That is why the subjunctive is natural here.

A learner can think of it this way:

• antequam + indicative: before something that actually happens / is presented as a fact
• antequam + subjunctive: before something expected, intended, or still in prospect

They are present subjunctive because the main verb dubitat is present, and the subordinate actions are viewed as contemporaneous with or subsequent to that present situation.

Latin sequence of tenses matters here:

• dubitat is a primary tense
• so subordinate subjunctives commonly use a present subjunctive for same-time or future-looking action

Thus:

• debeat = he should/ought to sign
• det = he gives / will give, in a subordinate setting after antequam

English may use different ways of expressing this, but Latin regularly uses the present subjunctive in this kind of primary sequence.

Formally, det is present subjunctive. In meaning, however, English will often express it as future:

• before he gives the money
• or more explicitly, before he will give the money / before he is to give the money

Latin does not have a future subjunctive, so the present subjunctive often covers situations that English feels are future from the point of view of the sentence.

Yes. Argentarius originally has to do with money and silver, and in context it can mean:

• banker
• moneylender
• financial agent

The exact English word depends on context. In many teaching sentences, banker is the simplest choice, but the broader financial sense is worth remembering.

Pactum is accusative singular because it is the direct object of signare.

You can see the relationship like this:

• signare = to sign
• what is signed? pactum

So pactum answers the question what? and therefore stands in the accusative.

Yes, but it is normal Latin specialness rather than anything unusual.

Latin word order is more flexible than English, so the sentence is arranged for style and clarity rather than because the grammar depends on position. Still, some points are worth noticing:

• Nemo dubitat comes first, establishing the main statement
• quin immediately signals the kind of subordinate clause that follows
• argentarius appears early in its clause, making the subject clear
• antequam pecuniam det comes at the end, where Latin often places time clauses

An English speaker may want to read word by word in order, but in Latin it is better to identify the clause structure first.

A very helpful way is:

• Nemo dubitat
• quin argentarius pactum signare debeat
• antequam pecuniam det

That gives you:

1. the main clause: no one doubts
2. the quin clause: that the banker ought to sign the agreement
3. the time clause: before he gives the money

This kind of chunking makes the sentence much easier to read than trying to translate each word one at a time.