IV–VI. Truth of the two natures in the incarnate person; divine and human
IV. In the incarnate person of Christ are contemplated the truth of the two natures, divine and human, and their personal union.
V. The divine nature in Christ is that by which He Himself, the eternal Son of God, personally united human nature to Himself. The divine nature, as the Leiden theologians rightly teach (Synopsis, disputation XXV, thesis 9), is not here properly understood as incarnate insofar as it is common to the three persons, but insofar as it is the Sons, distinct by a singular mode of subsistence — not as if the Deity of the Father and of the Holy Spirit were other and other, but because the Word of the essence is distinctly considered in the Son as communicated to Him from the Father by eternal generation (1 Timothy 3:16; Colossians 2:9; Proverbs 8:22-23; John 1:1,14; 8:58; Philippians 2:6). Orthodox theologians demonstrate this most solidly against Photinians, Arians, Servetists, and Socinians.
VI. The human nature in Christ is that which, absolute in all its essential parts and properties, was assumed by Him from the flesh of the virgin Mary into the unity of person. From this nature the Son of God is called made flesh (John 1:14) by synecdoche, as a whole human consisting of a true body and a rational soul — and indeed not excluding the humble and miserable condition and origin of humans (Philippians 2:7; John 1:14; 2 Corinthians 8:9; Hebrews 2:14; 4:15). Hence His genealogy is also led to Adam (Luke 3:38), against Marcion and the Manichees who invent Christs body as only apparent and simulated, and against the Valentinians who deny that Christ assumed His flesh from the substance of the virgin mother. Because He is a true human, He will have what constitutes a humans essence and without which to be human would involve a contradiction: namely an animated body and a rational soul endowed with intellect and will.
Latin
IV. In persona Christi incarnata spectantur duarum naturarum, divinae & humanae, veritas, earumque personalis unio. V. Divina natura in Christo est, qua ipse Filius Dei aeternus humanam naturam sibi personaliter univit. Natura divina, ut recte docent Theol. Leidenses synops. disp. XXV th. 9, non hic proprie intelligitur incarnata, qua tribus personis communis est, sed qua Filii est, singulari modo subsistendi distincta. Non quod alia atque alia sit Deitas Patris & Spiritus S., sed quod Verbum essentiae in Filio distincte consideretur, tanquam ipsi a Patre per aeternam generationem communicata, 1 Tim. 3:16; Col. 2:9; Prov. 8:22-23; Ioh. 1:1,14 & 8:58; Phil. 2:6 — id quod adversus Photinianos, Arianos, Servetistas & Socinistas orthodoxi Theologi solidissime demonstrant. VI. Humana natura in Christo est, quae ab eo omnibus partibus & proprietatibus essentialibus suis absoluta ex carne Mariae virginis in unitatem personae assumpta est. Ab hac natura Filius Dei dicitur caro factus Ioh. 1:14 per synecdochen, quippe integer homo corpore vero & anima rationali constans, & quidem non exclusa humili ac misera hominum conditione simul & origine, Phil. 2:7; Ioh. 1:14; 2 Cor. 8:9; Heb. 2:14 & 4:15. Unde & genealogia ipsius ad Adamum ducitur, Luc. 3:38, adversus Marcionem & Manichaeos, corpus Christi non nisi apparens & simulatum fingentes, & Valentinianos negantes Christum carnem suam e substantia virginis matris assumpsisse. Quia verus homo est, habebit quae hominis essentiam constituunt & sine quibus hominem esse contradictionem involveret; nimirum corpus animatum & animam rationalem, intellectu & voluntate praeditam.