The following quotes are taken from Eef Dekker’s Was Arminius a Molinist? The Sixteenth Century Journal, Vol. 27, No. 2 (Summer, 1996), pp. 337-352.
Arminius: 2. [He knows] all possibilia, which may refer as it were to three genera: [a]The first is [knowledge of those things, to which the power of God may immediately extend itself, or which may exist by an act performed by him alone. [b]The second is [knowledge] of those things which, by God’s conservation, motion, aid, concursuso, permission, can exist [as performed] by the creatures, whether these creatures will themselves exist or not, and whether they be placed in this or in that, or in infinitely many orders of things, [he knows] even those things which would exist by creatures, if this or that hypothesis were made. [c]The third is [knowledge] of those things which concerning the acts of creatures God can do — convenient for himself or for those acts. (Public Disputation, IV.34)
Dekker: Middle knowledge, we now see, is right at the heart of Arminius’ doctrine of divine knowledge. This conclusion is still reinforced by the fact that the traditional “middle knowledge” quotations from scripture, 1 Sam. 23:11-12 and Matt. 11:21, are not in the margin of thesis 43 (Public Disputation, IV.43), but precisely next to our text: in the margin of category 2[b] of thesis 34 (Public Disputation, IV.34).
Arminius: God’s knowledge which … is called “of simple intelligence” and natural or necessary is the cause of all things, by way of prescription and direction, to which is added the action of will and power, although it is necessary that middle knowledge intervenes in things which depend on freedom of created choice. (Public Disputation, IV.45)
Dekker: …Natural knowledge apparently cannot prescribe to the divine will how to proceed in case of human free will. The divine will needs middle knowledge in order to know which free human act can be realized, given certain circumstances. It needs no further comment when I say that this rationale was precisely that which Molina had in mind when he “invented” middle knowledge.
The following quotes are from Richard Muller’s God, Creation, and Providence in the Thought of Jacob Arminius: Sources and Directions of Scholastic Protestantism in the Era of Early Orthodoxy, Baker Book House, 1991:
By way of repudiating the Reformed view, Arminius would not only adopt a concept of scientia media, he would also argue an alternative view of concurrence…. Walaeus notes, however, that this hypothetical knowing is not necessarily to be understood as a third kind of knowledge separate from the scientia simplicis intelligentiae. Arminius argues precisely the point that the definitions offered by his Reformed contemporaries have purposely excluded. After his basic set of definitions, Arminius presents the thesis that:
The Scholastics say besides, that one kind of God’s knowledge is natural and necessary, another free, and a third intermediate (mediam). (1) Natural or necessary knowledge is that by which God understands himself and all possibilities; (2) free knowledge is that by which he knows all other beings; (3) middle knowledge is that by which he knows that “if this occurs, that will happen.” The first precedes every free act of the divine will. The second follows the free act of the divine will. This latter act indeed is preceded by the free will, but sees any future thing as a consequence of it … middle [knowledge] must intervene in things that depend on the freedom of creaturely choice. (Disp. Pub., Iv.xliii) (155-156)
Molina refers specifically to the statement of Origen that “a thing will happen not because God knows it as future; but because it is future, it is on that account known by God before it exists,” as cited by Aquinas, and specifically disagrees with Aquinas’ interpretation. Aquinas has categorically refused to view the future event as the cause of something in God or as standing outside of the divine causality … Arminius nowhere cites Driedo, Molina, Suarez, or Origen and nowhere notes the contemporary Roman Catholic debate over middle knowledge. His only citation of Aquinas stands in no direct relation to the question of scientia media, but it is hard to rule out the influence of Molina and Suarez on his doctrine.
There is even a hint of the famous Thomistic citation of Origen and its Molinst interpretation in Arminius’ remark that “a thing does not come to pass (non sit) because it is foreknown or foretold; but it is foreknown or foretold because it is yet to be (future est).” (Private Disputation, XXVIII.xiv) It is also the case that Arminius’ motivation in arguing the scientia media is identical with Molina’s: “the middle knowledge,” argues Arminius, “ought to intervene [i.e., between natural and free knowledge] in things which depend on the freedom of creaturely choice.” (Private Disputation, XVII.xii) Thus the scientia media must precede the act of will that grounds the scientia libera or scientia visionis, and must know future events, not because they have been willed but on the hypothesis of their future occurrence. God will, therefore, be able to ordain the means of salvation on the basis of a hypothetical or consequent knowledge of the creature’s fee choice in a context of grace. (160-161)
In its detail, Arminius’ language of the divine decrees veers away from the Suarezian view of predestination ante preavisa merita and evidences some affinity for both the teachings of Driedo and Molina and the formulation of Aquavia … Not only, moreover, can we assume that Arminius was aware of the general outlines of the Roman Catholic debate over grace, free will, and predestination, we can also infer from the catalogue of his library that he had a detailed, first-hand knowledge of the positions of Driedo and Molina and, probably of Suarez: he owned copies of Dreido’s De concorida liberi arbitrii et praedstinatioinis divinae (Louvain, 1537), Molina’s Concorida liberi arbitrii cum gratiae donis (Antwerp, 1595) and Suarez’ Opuscula theological. (163)
Thus, the divine will to save particular persons rests on the divine knowledge of future contingent acts — scientia media. Indeed, it is only by the device of scientia meida that Arminius can argue a genuinely universal will to save, resting on a knowledge of possibility and also argue, subsequently, a genuinely specific will to save believers only. (164)
Whereas the Reformed insisted upon the almost paradoxical point that an eternal and all-powerful God can in fact predetermine that some events will occur as a result of contingent or free acts of creatures and can therefore know such events according to his scientia libera seu visionis, Arminius follows Suarez in placing the divine foreknowledge or scientia media prior to the divine intervention, with the result that God can and does offer inducements to his creatures on the basis of his knowledge of their disposition towards or against certain acts. (260-261)