Was not St. Augustine, an orthodox Catholic bishop, author of the Calvinistic doctrine of predestination to hell?
No. Calvin certainly did not get that doctrine from St. Augustine, though he may have pretended to do so. G. P. Fisher, Protestant professor of Ecclesiastical History at Yale University, in his standard work “The History of the Christian Church,” page 321, says that Calvin, in his “Institutes,” went further than Augustine, declaring that sin, and consequently damnation, are the effect of an efficient decree of God. Now St. Augustine could not have taught that doctrine, if Calvin had to go further than Augustine in order to teach it! But let us go to St. Augustine himself. A man who believed that some men are predestined to hell no matter what they might do, could not possibly write as follows. In his book on “Catechizing the Ignorant,” St. Augustine writes, “The merciful God wishes to liberate men from eternal ruin, if they are not enemies to themselves, and do not resist the mercy of their Creator. For this purpose He sent His only-begotten Son.” Again he writes in his book “On the Sp