[I find helpful Oswald Bayer’s discussion of the relationship between Christianity and other religions]
The relation of the Christian faith to the other religions is not only problematic but also full of opportunity. Its claim to universality, however, does not give it the right to regard the truth claim of the other religions as indicative of an unbridgeable chasm separating them from Christianity. Indeed, the existence of the other religions is a reminder to us that Christian theology does not exist in a vacuum and there is no such thing as a pure theology that dialogues with itself in isolation from the conflicts and struggles of the world and its religions. On the other hand, the clear certainty of the Christian claim makes it impossible to transform this relationship into an apparently already existing identity, even if it is as Christologically grounded as Karl Rahner’s assumption of an “anonymous Christianity” in all religions. … [H]is assumption is thoroughly speculative and fails to recognize the importance of sin. We must avoid the identification that Rahner makes, as in his thesis of the anonymous Christian, just as strongly as the disjunction that others make, and recognize that we are in a situation of conflict in which truth and error are in contention. …
A key event, especially for the history of religion, and one that is very specific as well as being universal, is the union of divinity and humanity. This event is God’s physical and verbal self-communication in Jesus Christ. That explains why the image of God in humans is to be understood in a concrete physical way… theology attends first and last to the “form” by appreciating the bodily aspect of the word as much as the linguistic aspect of the body.
If, in light of the Christ event, God’s self-communication and its appropriation involves our senses, and if God’s goodness can be “tasted” (Ps. 34:8), it follows that one of the tasks of mission is to take seriously the rites and myths of the ethnic and world religions that in themselves are responses to God’s address with its appeal to the senses. However, in doing so, we must avoid starting with the idea of a general openness, in which the general closedness of humankind to God, which scripture calls sin (Gal. 3:23; Rom. 11:32), is not recognized.
This general closedness makes dialogue with other religions impossible insofar as a dialogue, at least according to the conventional understanding, assumes that the hidden truth, which always drives us to ask questions, will reveal itself little by little as we search for it together. This assumption of a general oppenness succumbs to the same illusion as the anticipation of a common understanding. … The alternative to dialogue is not domination but intercession in the solidarity spoken of in Romans 9:3. In the congregation’s intercession that grows out of learning through suffering, the church is there for others. [Oswald Bayer, Theology the Lutheran Way, 199-201]
Balaam's Ass 