Middle knowledge shares in both: free in its objects, natural in preceding every decree
They call God's knowledge of things that would happen contingently under some condition 'middle' because it neither fully matches the knowledge of vision nor the knowledge of simple intelligence, but shares something of each.
It is not about merely possible things considered apart from any question of existence, as the knowledge of simple intelligence is. Nor is it about things that will absolutely happen at some point in time by God's decree, as the knowledge of vision is.
In part it resembles free knowledge, because it concerns things that would happen freely if only the condition were met, and whether the condition is met lies in God's freedom. In part it resembles natural knowledge, because it comes before every decree of God, and God could not have been without it even if he had not decreed the world or decreed to create anything.
Latin
X. Scientia autem quam Deo tribuunt contingenter futurorum sub aliqua conditione, media ab illis vocatur, quoniam nec omnino convenit cum scientia visionis, nec etiam, cum scientia simplicis intelligentiae, sed de utraque aliquid participat. Nec enim est de rebus mere possibilibus, & abstracta ab omni consideratione existentiae, qualis est scientia simplicis intelligentiae: neque etiam est de rebus absolute futuris in aliqua temporis differentia, ex decreto Dei; qualis est scientia Visionis: Sed partim refert scientiam liberam, quia est de rebus libere futuris, si modo conditio poneretur, & in libertate Dei situm est, ut conditio illa ponatur: partim scientiam naturalem, quia praecedit omne decretum Dei, & Deus ea carere non potuit, etiamsi non decrevisset mundum, aut aliquid creare.