Joseph Bolin has asked me to collect as I go passages from Ratzinger about salvation outside the Church. He will teach a graduate course on this theme at the ITI this fall, and no doubt he will post about it on his blog.
If you go to Google Books, find The Mission and Nature of Theology, and perform a word search for “missionary”, you will find many of the texts I have come across recently. Click this link to see the results. While I do not want to type all of them out here, a good representative is the passage on page 25:
Whoever…would draw faith back into paradox or into a pure historical symbolism fails to perceive its unique historical position, whose defense engaged both the prophets and the apostles in equal measure. The universality of faith, which is a basic presupposition of the missionary task, is both meaningful and morally defensible only if this faith really is oriented beyond all symbolism of the religions toward an answer meant for all, an answer which also appeals to the common reason of mankind.
Throughout Ratzinger’s work from the 80s and 90s, one finds this emphasis on how Christian faith is different from myth in that it actually claims to offer truth to reason. In a few places, like this one, he draws out the consequence: if faith were a myth like other myths, missionary work would be indefensible; but because faith by its nature offers truth to reason, the Church by her nature is a missionary institution.
Ratzinger’s most extensive treatment of salvation outside the Church is found in Truth and Tolerance–see especially pages 202ff., but the theme comes up throughout. For those who want to find a few texts quickly, go to this book on Google Books and do word searches on “missionary” and then on “salvation”.
But because I have not yet reached Truth and Tolerance in my read-through, I will offer here a text from the book I am currently reading, Salt of the Earth. On page 23, Seewald asks whether other religions are equal to Catholicism, and Ratzinger responds rather firmly in the negative. Then on page 24, Seewald asks, “But could we not also accept that someone can be saved through a faith other than the Church?” Ratzinger responds:
That’s a different question altogether. It is definitely possible for someone to receive from his religion directives that help him become a pure person, which also, if we want to use the word, help him to please God and reach salvation. This is not at all excluded by what I said; on the contrary, this undoubtedly happens on a large scale. It is just that it would be misguided to deduce from this fact that the religions themselves all stand in simple equality to one another, as in one big concert, one big symphony in which ultimately all mean the same thing.
Religions can also make it harder for man to be good. This can happen even in Christianity because of false ways of living the Christian reality, sectarian deformations, and so forth. In this sense, in the history and universe of religions, there is always a great necessity to purify religion so that it does not become an obstacle to the right relation to God but in fact puts man on the right path.
I would say that if Christianity, appealing to the figure of Christ, has claimed to be the true religion among the religions of history, this means [in connection with what I have just said] that in the figure of Christ the truly purifying power has appeared out of the Word of God. Christians do not always live this power well and as they should, but it furnishes the criterion and the orientation for the purifications that are indispensable for keeping religion from becoming a system of oppression and alienation, so that it may really become a way for man to God and to himself.