With everything else that's been going on recently, the Jewish blogosphere has been burning up with the question: What are the proper parameters for Orthodox involvement in Inter-faith dialogue, and what degree of theological flexibility do those involved in such activity have?
The issue is extremely thorny, and a blog posting is not the place to responsibly discuss so important an issue. Certain salient points, though, are appropriate in this context.
1) The best point of departure remains Rabbi Soloveitchik's essay, Confrontation, (and see the important observations of Rabbi Professor David Berger, here). The leitmotif of that essay was the absolute need to respect the inviolate nature of the faith commitment of one's Christian/Muslim/Hindu/Buddhist interlocutor. In other words, it is both disrespectful (and futile) to engage a believer on the central issues of their faith. Thus, to argue that Jesus was simply a Pharasaic fellow traveller, or that Jerusalem had little or no religious significance for Muslims until after the First Crusade, is to simply indulge in a dialogue of the deaf (at best). Jews might believe either or both to be true. That is irrelevant, and such discussions should best be kept off of the agenda.
2) There are broad swaths of thought and action where members of different faith committments can find common ground. The struggle against neo-paganism (aka secular humanism) comes to mind. Even political issues can be put on the agenda, without venturing into core issues that divide us. For example, Evangelical Christians and Jews share a non-allegorical approach to the Prophetic promises regarding Israel's return to its ancestral homeland, and the role of that return in improving the moral standing of mankind. Where there is a clear common language, where the innermost truths of a faith community are not in play, there is a place for mutually respectful conversation.
3) Most importantly, such encounters are no place for tyros. In line with Judah Ibn Tibbon's rules for proper translation, one who is involved must have total mastery of his own tradition and extensive expertise in that of his interlocuter's tradition. Anything less is simply unacceptable.
Hazal taught that anyone who is unfamiliar with the nature of Gittin and Qiddushin should not involve himself therewith (Gittin 5b). The same is definitely true when representing Judaism in an encounter with outher religions.