The Virgin is the conqueror of all heresies

As a young theologian in the time before (and also during) the Council, I had, as many did then and still do today, some reservations in regard to certain ancient formulas, as, for example, that famous De Maria nunquam satis, 'concerning Mary one can never say enough.' It seemed exaggerated to me. So it was difficult for me later to understand the true meaning of another famous expression (current in the Church since the first centuries when — after a memorable dispute — the Council of Ephesus, in 431, had proclaimed Mary Theotokos, Mother of God). The declaration, namely, that designated the Virgin as 'the conqueror of all heresies'. Now — in this confused period where truly every type of heretical aberration seems to be pressing upon the doors of the authentic faith — now I understand that it was not a matter of pious exaggerations, but of truths that today are more valid than ever.

The Ratzinger report : an exclusive interview on the state of the Church by Joseph Ratzinger, Joseph and Vittorio Messori, Leominster, Herefordshire : Fowler Wright Books, 1985, p. 105-106