The consideration of these serious difficulties leads us to the very heart of Molina’s system, and reveals the real Gordian knot of the whole controversy. For Molinism attempts to meet the objections just mentioned by the doctrine of the Divine scientia media. Even Molinism must and does admit that the very idea of efficacious grace includes the free consent of the will, and also that the decree of God to bestow an efficacious grace upon a man involves with metaphysical certainty the free co-operation of the will. From this it follows that God must possess some infallible source of knowledge by means of which he knows from all eternity, with metaphysical certainty, whether in the future the will is going to co-operate with a given grace or to resist it. When the question has assumed this form, it is easy to see that the whole controversy resolves itself into a discussion on the foreknowledge which God has of the free future acts; and thus the two opposing systems on grace are ultimately founded upon the general doctrine on God and His attributes. Both systems are confronted with the wider and deeper question: What is the medium of knowledge (medium in quo) in which God foresees the (absolute or conditioned) free operations of His rational creatures? That there must be such a medium of Divine foreknowledge is evident. The Thomists answer: God foresees the (absolute and conditioned) free acts of man in the eternal decrees of His own will, which with absolute certainty produce prœmovendo as definite prœdeterminationcs ad unum, all (absolute and conditional) free operations. With the same absolute certainty with which He knows His own will, He also foresees clearly and distinctly in the decrees of His will all future acts of man. However, the Molinists maintain that, since, as we remarked above, the predetermining decrees of the Divine Will must logically and necessarily destroy freedom and lead to Determinism, they cannot possibly be the medium in which God infallibly foresees future free acts. Rather these decrees must presuppose a special knowledge (scientia media), in the light of which God infallibly foresees from all eternity what attitude man’s will would in any conceivable combination of circumstances assume if this or that particular grace were offered it. And it is only when guided by His infallible foreknowledge that God determines the kind of grace He shall give to man. If, for example, He foresees by means of the scientia media that St. Peter, after his denial of Christ, shall freely co-operate with a certain grace, He decrees to give him this particular grace and none other; the grace thus conferred becomes efficacious in bringing about his repentance. In the case of Judas, on the other hand, God, foreseeing the future resistance of this Apostle to a certain grace of conversion, decreed to allow it, and consequently bestowed upon him a grace which in itself was really sufficient, but remained inefficacious solely on account of the refractory disposition of the Apostle’s will. Guided by this scientia media God is left entirely free in the disposition and distribution of grace. On His good pleasure alone it depends to whom He will give the supreme grace of final perseverance, to whom He will refuse it; whom He will receive into Heaven, whom He will exclude from His sight for ever. This doctrine is in perfect harmony with the dogmas of the gratuity of grace, the unequal distribution of efficacious grace, the wise and inscrutable operations of Divine Providence, the absolute impossibility to merit final perseverance, and lastly the immutable predestination to glory or rejection; nay more, it brings these very dogmas into harmony, not only with the infallible foreknowledge of God, but also with the freedom of the created will. The scientia media is thus in reality the cardinal point of Molinism; with it Molinism stands or falls. This doctrine of the scientia media is the battlefield of the two theological schools; the Jesuits were striving to maintain and fortify it, while the Dominicans are ever putting forth their best efforts to capture or turn the position. The theologians who have come after them, unhampered by the traditions of either order, have followed some the doctrine of the Jesuits, some the Dominican system.