JOHN ANKERBERG: Now, Dr. John MacArthur, when we met together, we agreed that the ECT document, the “Evangelicals and Catholics Together” document was attempting to join Roman Catholics and Evangelical Protestants together as “cobelligerents,” the word the Francis Schaeffer coined “working at the grass-roots level” in terms of social issues.

And we were going to work together against the many social evils, including secular humanism, the riding tide of Islam, pornography, abortion, and things like that. But we also agreed that this work [ECT] has been perceived as going too far in proclaiming the kind of unity that exists. I would like you to define the kind of unity that can exist between Evangelicals and Roman Catholics, and the kind of unity that cannot exist until the doctrine of “Justification by faith alone” has been dealt with clearly. 

JOHN MACARTHUR: Look, if the Catholic Church is already a cobelligerent, if they are already anti-abortion, and pornography, and homosexuality; they are going to use all of their energies within the framework of their system to go after that. We are committed to that, and we are going after that. There is already a collective movement. Once you then sort of try to define that as “common spiritual mission” built on “common spiritual unity” you just take doctrine and throw it out the window, and perception is violated, particularly because the Catholic Church claims to be true Christianity, and when we reverse 450 years of history, and just throw our arms around the Roman system, which I think we have to say, John, in all honesty, is not a group of wayward brothers but is an apostate form of Christianity. It is a false religion, it is another religion.

When you throw your arms around that you literally have to undo any doctrinal distinction. In fact, ECT doesn’t just do that implicitly, they do that explicitly. In the document, in effect, they say, “we have to accept all baptized Roman Catholics as brothers and sisters in Christ.” In an article that followed that up in Christianity Today, J. I. Packer said, “We should acknowledge as brothers and sisters in Christ, anyone who lives to the highest ideals of their communion.” My response to that is the opposite. I maybe could fellowship with a bad Roman Catholic, that is, one who has rejected the system, but was still in the church and came to know Christ. But one who holds the highest ideals of Roman Catholicism—on what grounds do I have spiritual unity?

And when you get spiritual leaders from both churches, coming together to sign a common effort—you may say that it is to fight a cultural war, but people are going to see it as confusion over doctrine. Well, I might be a little bit radical on this, but I will go ahead. I think the way we can work together on it is for the Catholics to work against those things, like they want to work against them, and we will work against those things, like we want to work against them, but we can’t really throw our arms around each other in a common effort because that confounds the issue of spiritual truth. (Irreconcilable Differences: Catholics, Evangelicals, and the New Quest for Unity) 

See also:

ROMAN CATHOLICISM HAS A DIFFERENT GOSPEL

WHAT DOES THE ROMAN CATHOLIC CHURCH TEACH ABOUT THE DOCTRINE OF JUSTIFICATION?

HAS THE ROMAN CATHOLIC CHURCH REALLY CHANGED?