Argument from reason: conditional propositions about future contingents are determinately true or false
They also think many arguments from reason prove that God has such knowledge. The first is this. Propositions about a future contingent under some condition have determinate truth or falsity, just as much as propositions about things that will absolutely happen. So they too are objects of God's knowledge, since no truth can be hidden from an infinite intellect, which the divine intellect is.
That propositions about future contingents under a condition are determinately true or false follows from the fact that there can be genuine contradiction between them, just as between propositions about things that will absolutely happen. These two plainly contradict each other: 'If Peter is placed in such circumstances, he will sin' and 'It is not the case that if Peter is placed in such circumstances, he will sin.' In every pair of contradictories one side must be true and the other false.
Latin
XV. Praeterea multis argumentis ex ratione ductis probari posse putant talem scientiam in Deo reperiri. Et primo quidem inde quod in propositionibus de futuro contingenti sub aliqua conditione determinata est veritas, vel falsitas, non minus quam in propositionibus de iis quae sunt absolute futura; ac proinde sunt illae quoque scientiae divinae objectum: quandoquidem nulla veritas latere potest intellectum infinitum, qualis divinus est. Propositiones autem de futuris contingentibus sub aliqua conditione determinate veras, vel falsas esse, ex eo conficitur quod inter eas vera potest esse contradictio, haud secus ac inter eas quae sunt de rebus absolute futuris. Siquidem prorsus haec sibi contradicunt, Si Petrus in talibus circumstantiis ponatur, peccabit, Et, Non si Petrus in talibus circumstantiis ponatur, peccabit. In omnibus autem contradictoriis, necesse est alteram partem contradictionis veram, alteram falsam esse.