Demonstration: Scripture, the Name, reason from independence
But we demonstrate that God is an absolutely necessary being, FIRST, by the testimonies of sacred Scripture (1 Timothy 6:16-17; Romans 1:23; Psalm 102:27-28), where God is called immortal and incorruptible and is opposed to corruptible things, and is established always to remain, to declare absolute necessity of existing. From which also Augustine (On the Trinity 1.1): Although, he says, the soul is said to be immortal in a manner, the Apostle would not say, Who alone has immortality, unless because true immortality is incommutability, which no creature can have, since it belongs to the Creator alone.
SECOND, by the Name of God, Eheje (Exodus 3:14), by which absolute necessity of existing is indicated, as Nazianzen (Oration 24 / 2 on theology) and Augustine (On True Religion, chapter 49) testify. For this reason God also attributes Being to Himself alone, as He who alone is necessarily (Isaiah 42:8; Amos 5:8).
THIRD, by reason. For every independent being, and what exists from itself, is absolutely necessary. God is an independent being, existing namely from Himself, as was demonstrated in chapter 2 on God's existence. Therefore God is an absolutely necessary being.
Latin
DEMONSTRAMUS autem Deum esse ens absolute necessarium, PRIMO, sacrae Scripturae testimoniis, 1 Tim. 6.16.17; Rom. 1.23; Psal. 102.27.28, ubi Deus immortalis & incorruptibilis dicitur ac rebus corruptibilibus opponitur, semperque permanere statuitur ad declarandam absolutam exsistendi necessitatem. Unde & Augustinus lib. 1. de Trin. cap. 1: Cum, inquit, anima quodammodo immortalis esse dicatur, non diceret Apostolus, Qui solus habet immortalitatem, nisi quia vera immortalitas incommutabilitas est, quam nulla habere potest creatura, quoniam solius creatoris est. SECUNDO, Nomine Dei, Eheje, Exod. 3.14. quo absoluta exsistendi necessitas indicatur, ut testatur Nazianzenus Orat. 24. sive 2. de theol. & August. lib. de vera relig. cap. 49. Hacpropter Deus etiam sibi soli ipsum esse attribuit, tanquam qui solus sit necessario, Esai. 42.8; Amos 5.8. TERTIO, ratione. Omne enim ens independens, atque quod a se exsistit, est absolute necessarium. Deus est ens independens, exsistens nimirum a seipso, ut demonstratum est cap. 2. de Dei exsistentia. Ergo Deus est ens absolute necessarium.