It is my understanding that Calvinism conflates God's passive will with His active will—i.e., the fact that He knows something will occur due to His divine foreknowledge and allows said thing to occur is taken to mean that He actively wills said thing. It also seems to me that it mostly goes beyond Saint Augustine's own teachings on predestination and free will.
However, Oxford theologian J.N.D. Kelly writes the following on Augustine in Early Christian Doctrines XIII.7:
God's choice of those to whom grace is to be given in no way depends on His foreknowledge of their future merits, for whatever good deeds they will do will themselves be the fruit of grace. In so far as His foreknowledge is involved, what He foreknows is what He Himself is going to do. [emphasis mine]
I am having a hard time seeing how these writings could not lend support to Calvinism's equating of God's foreknowledge with active predestination. Is it possible to reconcile them with the Catholicism that claims Augustine as one of its greatest saints?