MCT 4-level sentence analysis for a 13-year-old — Augustine-style Latin sentence broken down (Quoniam de civitatis utriusque ... clarescat)

I'll explain this sentence step by step, in four levels. First I give a short literal translation and plain-paraphrase. Then I show the clause structure (who does what), the phrase roles (subject, object, etc.), and finally the key words with their grammar so you can see how the parts fit.

Short literal translation (one sentence): "Because I must now discuss about the duties and limits of both cities, earthly and heavenly, first the arguments of men must be set out as far as the plan for finishing this work allows — the arguments by which they tried to make happiness for themselves in the misery of this life — so that it may be clear how our hope differs from their vain things, and what the thing itself, that is true beatitude which He will give, is; and that this be made clear not only by divine authority but also by reason of the kind we can use because of unbelievers."

Plain-paraphrase (easier): "I need to talk about the limits and duties of both the earthly and heavenly city. Before I do that, I should explain, as much as my plan allows, the ideas people have used to try to be happy in this unhappy life. I explain them so we can see how our hope is different from their empty hopes, and so we can understand what true happiness is that God will give — and to show this not only by referring to God, but also by using reason that can persuade non-believers."

1. Level 1 — Main structure (big-picture)
   • Main idea introduced by Quoniam (because): the speaker says why he must speak: "deinceps mihi vӕdeo disputandum" — "I see that I must argue (discuss) next."
   • Then comes an instruction: "prius exponenda sunt ..." — "first must be explained ..." (this depends on the first idea: before arguing, he must explain some things).
   • The final goal is given by an ut-purpose with the verb clarescat (let it be made clear) — i.e. the explanations are given so that something becomes clear.
2. Level 2 — Clause map (who does what and how clauses connect)
   1. Quoniam de civitatis utriusque, terrenae scilicet et caelestis, debitis finibus, deinceps mihi video disputandum.
      • Type: main clause introduced by causal "Quoniam" (because). Verb: video + gerundive/infinitive idea disputandum = "I see that I must argue next about ..." The object/topic of that arguing is given by the following phrase de civitatis ... finibus (about the limits/duties of both cities).
   2. prius exponenda sunt quantum operis huius terminandi ratio patitur,
      • Type: principal action that follows: "first must be explained (prius exponenda sunt) as far as the plan of finishing this work allows". This tells us we must explain something before arguing further.
   3. argumenta mortalium quibus sibi ipsi beatitudinem facere in huius vitae infelicitate moliti sunt,
      • Type: the thing to be explained — "the arguments/opinions of mortal men". This is modified by the relative clause quibus ... moliti sunt meaning "by which they attempted to make happiness for themselves in the miseries of this life."
   4. ut ab eorum rebus vanis spes nostra quid differat quam deus nobis dedit,
      • Type: purpose clause introduced by ut. Purpose: "so that it may be clear how our hope differs from their vain things more than what God gave us" — more smoothly: "so we can see how our hope is different from their empty hopes, and how it compares to what God gave us." This ut-clause links to the verb clarescat at the end.
   5. res ipsa, hoc est vera beatitudo, quam dabit,
      • Type: continuation inside the purpose: "the thing itself, that is true beatitude, which He will give" — this names the positive goal: the true happiness God gives, whose nature should be made clear.
   6. non tantum auctoritate divina, sed adhibita etiam ratione qualem propter infideles possumus adhibere, clarescat.
      • Type: final comment that completes the ut ... clarescat idea: "let it be clear not only by divine authority but also by reason (the kind of reason we can use because of unbelievers)." The verb clarescat (subjunctive) is the main verb of the whole ut-purpose.
3. Level 3 — Phrases and their grammatical roles (short and simple)
   • de civitatis utriusque, terrenae scilicet et caelestis, debitis finibus — prepositional phrase "about the duties/limits of both cities (the earthly and the heavenly)". This is the topic of the later arguing (disputandum).
   • deinceps mihi video disputandum — literal: "henceforth to me it must be argued/it seems I must argue". Speaker = mihi (to me / I must), action = argue.
   • prius exponenda sunt — passive-periphrastic sense: "must first be set out/explained". Something must be explained before proceeding.
   • quantum operis huius terminandi ratio patitur — limiting phrase: "as much as the plan/method of completing this work allows" (how much the project permits us to explain now).
   • argumenta mortalium — "the arguments/opinions of mortal people" — the direct thing to explain (subject of "exponenda sunt").
   • quibus ... moliti sunt — relative clause modifying argumenta: "by which they tried/struggled to make themselves beatitude/happiness".
     • sibi ipsi beatitudinem facere = "to make happiness for themselves" (infinitive phrase showing purpose of their effort).
     • in huius vitae infelicitate = "in the unhappiness of this life" (where they tried to find happiness).
   • ut ... clarescat — purpose clause: "so that it may be made clear". Inside it we find two things the speaker wants clear:
     • how our hope differs from their vain things (ut ab eorum rebus vanis spes nostra quid differat),
     • and what the true beatitude is that God will give (res ipsa, hoc est vera beatitudo, quam dabit).
   • non tantum ... sed adhibita etiam ratione ... clarescat — "let it be clear not only by divine authority but also by reason (the kind usable because of unbelievers)" — describes the kinds of proof the speaker will present.
4. Level 4 — Key words and grammar (quick list, helps translation)
   • Quoniam — because (causal conjunction).
   • de + ablative (civitatis ... finibus) — about / concerning the limits/duties of the city.
   • utriusque — of both (refers to two cities: earthly and heavenly).
   • deinceps — henceforth / next.
   • mihi video disputandum — "I see that I must discuss" (video + gerund/gerundive sense).
   • prius exponenda sunt — "must first be explained" (exponenda sunt = it must be set forth; gerundive/impersonal passive sense).
   • quantum ... patitur — "as much as ... allows" (quantum + verb = how much).
   • argumenta mortalium — "the arguments of men" (nominative plural: subject of exponenda sunt).
   • quibus ... moliti sunt — "by which they strove/attempted" (relative pronoun + perfect verb; explains purpose of arguments).
   • sibi ipsi beatitudinem facere — "to make happiness for themselves" (infinitive phrase showing goal).
   • ut ... clarescat — purpose clause, clarescat = present subjunctive meaning "may be made clear".
   • res ipsa, hoc est vera beatitudo, quam dabit — "the thing itself, that is true beatitude which He will give" (apposition: hoc est explains res ipsa).
   • non tantum ... sed ... etiam — not only ... but also (contrast: divine authority vs. reason usable with unbelievers).

How to study a sentence like this (tips):

1. Find the main verbs (here: video, exponenda sunt, clarescat).
2. Mark connectors: Quoniam (because), prius (first), ut (so that/purpose), sed (but).
3. Identify the big noun phrases (topic: de civitatis utriusque ... finibus, thing to explain: argumenta mortalium, goal: res ipsa (vera beatitudo)).
4. Translate small chunks and then put the chunks together into the full sentence.

If you want, I can now show a word-for-word literal translation line by line, or draw a simple tree diagram of the clauses. Which would help you more?