Christianae religionis reuerentiam plures usurpant, sed ea fides pollet maxime ac solitarie quae cum propter uniuersalium praecepta regularum, quibus eiusdem religionis intellegatur auctoritas, tum propterea, quod eius cultus per omnes paene mundi terminos emanauit, catholica uel uniuersalis uocatur. Cuius haec de trinitatis unitate sententia est: "Pater," inquiunt, "deus filius deus spiritus sanctus deus." Igitur pater filius spiritus sanctus unus non tres dii. Cuius coniunctionis ratio est indifferentia. Eos enim differentia comitatur qui uel augent uel minuunt, ut Arriani qui gradibus meritorum trinitatem uariantes distrahunt atque in pluralitatem diducunt. Principium enim pluralitatis alteritas est; praeter alteritatem enim nec pluralitas quid sit intellegi potest. Trium namque rerum uel quotlibet tum genere tum specie tum numero diuersitas constat; quotiens enim idem dicitur, totiens diuersum etiam praedicatur. Idem uero dicitur tribus modis: aut genere ut idem homo quod equus, quia his idem genus ut animal; uel specie ut idem Cato quod Cicero, quia eadem species ut homo; uel numero ut Tullius et Cicero, quia unus est numero. Quare diuersum etiam uel genere uel specie uel numero dicitur. Sed numero differentiam accidentium uarietas facit. Nam tres homines neque genere neque specie sed suis accidentibus distant; nam uel si animo cuncta ab his accidentia separemus, tamen locus cunctis diuersus est quem unum fingere nullo modo possumus; duo enim corpora unum locum non obtinebunt, qui est accidens. Atque ideo sunt numero plures, quoniam accidentibus plures fiunt.
There are many who claim as theirs the dignity of the Christian religion; but that form of faith is valid and only valid which, both on account of the universal character of the rules and doctrines affirming its authority, and because the worship in which they are expressed has spread throughout the world, is called catholic or universal. The belief of this religion concerning the Unity of the Trinity is as follows: the Father is God, the Son is God, the Holy Spirit is God. Therefore Father, Son, and Holy Spirit are one God, not three Gods. The principle of this union is absence of difference[10]: difference cannot be avoided by those who add to or take from the Unity, as for instance the Arians, who, by graduating the Trinity according to merit, break it up and convert it to Plurality. For the essence of plurality is otherness; apart from otherness plurality is unintelligible. In fact, the difference between three or more things lies in genus or species or number. Difference is the necessary correlative of sameness. Sameness is predicated in three ways: By genus; e.g. a man and a horse, because of their common genus, animal. By species; e.g. Cato and Cicero, because of their common species, man. By number; e.g. Tully and Cicero, because they are numerically one. Similarly difference is expressed by genus, species, and number. Now numerical difference is caused by variety of accidents; three men differ neither by genus nor species but by their accidents, for if we mentally remove from them all other accidents,[11] still each one occupies a different place which cannot possibly be regarded as the same for each, since two bodies cannot occupy the same place, and place is an accident. Wherefore it is because men are plural by their accidents that they are plural in number.