Ye Shall Know the Truth: Christianity and the Perennial Philosophy
The Perennial Philosophy referred to here is generally the philosophy espoused by the Catholic Church in the Middle Ages. To the extent that other religious traditions approximate to this point of view, they are considered to be part of the Divine Truth. This leads to some highly refined interpretations and rather selective readings of other faiths as the search is made to find the thread of Perennial Philosophy supposedly running through all worthwhile thought. --Catholic Library World  December 2007