Mary is only intelligible in terms of Christ. If someone does not hold with the Catholic faith that the Word of God became man in Adam’s flesh so that the world might be taken up redemptively into the life of God, he can have no understanding of Catholic dogma about Mary either. It may indeed be said that a sense of Marian dogma is an indication of whether Christological dogma is being taken really seriously; or whether it is being regarded (consciously or unconsciously) merely as a rather outmoded, problematic, mythological expression of the fact that in Jesus (who is basially just a religious man) we undoubtedly feel God (here again a cipher for an unexpressed mystery) particularly close to us. No, this Jesus Christ, born of Mary in Bethlehem, is at once, as One and Indissoluble, true man and true Word, consubstantial with the Father. And so Mary is in truth the Mother of God. It is only to someone who truly and unreservedly confesses this that the Catholic Church can continue to speak meaningfully about her other Marian dogmas. And if anyone protests against further Marian dogmas, either explicitly or by passive indifference, he must expect to be asked whether he believes and confesses what the Church solemnly confessed at Ephesus in 431 as the faith of the one and undivided Church, and what the Reformed Church of the sixteenth century believed too, though it did not really raise the question whether this was necessary in order that one could as a sinner be consoled by faith in a gracious God.
— Karl Rahner, Theological Investigations, I:202-203 (Kjelde: Pontifications)