XI–XIII. Personal union; ineffable mode neither essential nor accidental
XI. Personal union is that by which the Son of God joined the assumed nature to Himself into the unity of His person. XII. In it are contemplated mode and effect.
XIII. Although the mode is ineffable, it is denied to be a conjunction or union that is either essential — by which things having a mutual and natural respect to one another are united, as act and potency, matter and form, genus and specific difference — or accidental, by which either accidents are joined to subjects or substances themselves are accidentally joined among themselves: but personal, by which in the personality of the Word as a common bond distinct natures, not inclining by any natural tendency to union, are gathered into one — a union whose like is not found in the whole nature of things — against Eutyches confusing the natures and Nestorius tearing them apart and wrongly dissolving the unity of Christs person.
Since therefore there is one personality of both natures, there is also one person and one personal union (1 Corinthians 8:6; John 20:31; 1 John 4:15; John 9:37).
Latin
XI. Unio personalis est, qua Filius Dei naturam assumptam sibi in personae suae unitatem coniunxit. XII. In ea spectatur modus & effectus. XIII. Modus quamvis ineffabilis sit, tamen negatur esse coniunctionem sive unionem eamque neque essentialem, qua quae mutuum & naturalem respectum habent ad se invicem uniuntur, ut actus & potentia, materia & forma, genus & differentia specifica; neque accidentalem, qua vel subiectis accidentia, vel ipsa substantia inter se accidentaliter coniunguntur: sed personalem, qua in personalitate Verbi tanquam communi vinculo naturae distinctae, & nulla naturali inclinatione ad unionem propendentes, in unum colligantur, cuius unionis similis alia non invenitur in universa rerum natura — contra Eutychen naturas confundentem & Nestorium eas distrahentem & unitatem personae Christi perperam dissolventem. Quoniam igitur una utriusque naturae est personalitas, idcirco & una est persona & personalis unio, argumento 1 Cor. 8:6; Ioh. 20:31; 1 Ioh. 4:15; Ioh. 9:37.