Many of our graduates have been want to set up a radical opposition between the Catholic understanding of grace and that of 'Protestantism.' Now, it depends what you mean by Protestantism in the first place - Lutheran or Reformed. Lutheranism hardly differs at all from the Catholic understanding of grace and the means of salvation. Calvinism is a hard-lined Augustinianism which differs from Aquinas' hard-lined Augustinianism, but not as much as one would assume. In fact, many assume that Calvin's is the correct interpretation of Augustine, with Aquinas falling off from it somewhat. I do not. It might be hard to figure out how it was logically possible for Augustine not to teach double-predestination (the hallmark of Calvinism), but he did not, nor for that matter did Aquinas. Double-predestination means that God positively wants people to go to hell: God created people with the express purpose in mind of damning them. This, however, cannot be, since God only wills damnation for the good of punishing evil He absolutely cannot will in itself. De Lubac is right to regard this kind of thinking as a day and night kind of difference in spirit.
Another thing. I have heard from several of our graduates (and form this student yesterday) that these Calvinists refer to the Catholics as 'dualists.' For the life of me I cannot figure out what they could possibly mean by this. I will take my best guess: they think we hate the body because of our ascetic tradition (i.e. our praise of celibacy), a tradition which Luther anyway rejected? If this is their reasoning, I find it rather an ironic suggestion. After all, Augustine (whom their Calvin loved above all!) of all the Church Fathers was most blamed for dualism. Julian of Eclanum, the Pelagian, called Augustine a dualist because of his doctrine of original sin - which doctrine all the mainstream churches accept (Catholic, Lutheran, Reformed). Julian thought Augustine thought evil must be a substance because it was not something specifically reducible to my actual sin, i.e., I was 'guilty' or 'infected' with original sin but I did not actually 'do' the sin. On top of this, Augustine thought original sin was passed on through carnal concupiscence (sex). Thus, putting two and two together, these Ancasterian Calvinists must think that we teach the superiority of celibacy over marriage between sex is infected. What is surprising is that they don't realize that we get this from the same place they get their doctrine of original sin - Augustine. The only difference is we think celibacy is better than marriage. Their error lies in not seeing how the Catholic position is somewhat more consistent. Why do not Protestants see that an ascetic attitude makes sense given the doctrine of original sin? Of course, their fundamental intuition lies with Luther's condemnation of works, regardless of any other consideration. So much is this so that I have encountered so many learned Protestants who cannot in any way see that asceticism has roots in the New Testament.
But ignorance has an ecumenical character. Many of my ex-students are under the impression that the difference between Catholicism and Protestantism is the difference between advocacy of free will verses advocacy of determinism. Thus do they greet Thomas' treatise on predestination with a great deal of head-scratching.
My one ecumenical lesson is this: the other side is not filled with idiots. There are plenty on both sides. It is not always easy to determine over what precisely Christians differ. Of course, sometimes it is.