Interfaith engagement has tended to take one of three major patterns in Christian history. We're right and you are wrong, a black and white view of the world which fails to do justice to kalidescopic colours of life. A successionist view of religions, which sees one succeeding the other - problematic for Christians engaging with Islam or a relativism which says that we are all heading for the some goal and it doesn't matter which way we go. This is an approach that evades the question of truth and similarly overlooks the fact that different religious traditions have very different views about the goal of life and the character of what virtues we need to develop on our way to the goal.
Jim Barr in his sermon on Romans 11 at Canberra Baptist Church this morning argues that the way to interfaith engagement begins with "the place where we are wrong". For Christians this means an engagement that begins with confession of our implication as a community of faith with the state use of violence through the Christendom era and into the period of colonialism.
Following from Jim's suggestion it would seem that we do not so much need a theory about other "schools of faith" whether liberal or fundamentalist, but rather a communal practice of confession and opening our hands to receive the grace of God's mercy and forgiveness - even from hands of those who have suffered at the hands of our fellow members of Christ's body.