One God vs many gods; Trinity beyond demonstration from cause or effects
It is indeed of the same madness to acknowledge no God and to assert many gods with the ancient Sabaeans, in Averroes and Maimonides, to whom Moses law was chiefly opposed — Deuteronomy 6:4. We understand God to be one when we understand that He is, as our weakness bears. For that must be unique which is best, greatest, and most perfect. Nor is he highest who has a superior or equal. And if two are set as equals, neither will be highest.
Therefore we no less execrate the delirium of Cerdo, Marcion, and the Manichees bringing in two gods unequal in nature and office, than either the Valentinians multiple offspring of Aeons, or the Sabaeans and other pagans innumerable swarms of deities. But that the same is threefold in persons is a secret unsearchable to human reason, to be adored with humble faith and piety, not searched with curious or scrupulous rashness.
For this Trinity can neither be demonstrated from its cause, which it has none, nor from effects, which do not declare this distinction of persons precisely and evidently, but only what belongs to each person. But whatever may be learned of this secret is to be learned from Gods word, and one must piously rest in the measure of this divine revelation.
Latin
Ejusdem profecto insaniae est, nullum Deum agnoscere et plures Deos asserere cum Zabaitis priscis, apud Averroem et Maimonidem, quibus lex Mosis potissimum opposita fuit — Deut. VI.4. Deum unum esse intelligimus, cum quod sit, ut fert imbecillitas nostra, intelligimus. Unicum enim esse necesse est, quod optimum, maximum, atque perfectissimum est. Neque summus est, qui superiorem vel parem habet. Ac duo, si pares statuantur, summus neuter erit. Quapropter haud minus execramur Cerdonis, Marcionis et Manichaeorum duos natura officioque dispares Deos invehentium delirium, quam vel Valentinianorum multiplices Aeonum foetus, vel Zabiorum aliorumque ethnicorum innumera numinum examina. At eundem personis trinum esse, arcanum est humanae rationi impervestigabile, humili fide et pietate adorandum, non curiosa aut scrupulosa sive temeritate perscrutandum. Haec enim Trinitas neque demonstrari potest a causa sua, quam nullam habet: neque ab effectibus, qui non hanc personarum distinctionem praecise et evidenter, sed id tantum quod cuilibet personae competit, declarant. Quicquid vero de hoc arcano discere licet, id ex Dei verbo discendum, moduloque divinae hujus revelationis pie acquiescendum est.