Here we are concerned with only those aspects that characterize the mystery of the (Roman) Catholic Church vis--vis the other Christian denominations, i.e., things which, in ecumenical dialogue, Catholics are often more reluctant to mention and which they try to play down. There are two ways of doing the reverse, of showing that such things are often central. There is the "counter-Reformation" way of polemics, meeting assertions with counter-assertions; and there is the genuinely Catholic way, which starts out from the mystery affirmed by both parties and endeavors on this basis to show the distinctively Catholic teaching, so that, from his own standpoint, the non-Catholic partner-in-dialogue is able to see the inner connections. This is neither "controversy", therefore, nor diplomatic "irenicism", nor some neutral "comparative study of denominations", but a reflection that can call itself ecumenical because it is Catholic.