This question keeps coming up. So here’s the best way I can explain it.

First, the prefix matters. “INTER” means “between,” “among,” “in the midst of,” “mutually,” “reciprocally,” “together.”INTERfaith is different religions being together.

“INTRA” means  “within, inside, on the inside.” INTRAfaith is one religion examining just itself in light of its INTERfaith experience.

Here’s how John Dunne puts it. In his book, The Way of All the Earth, he describes the 2-way process of interfaith engagement:

“What seems to be occurring is a phenomenon we might call ‘passing over,’ passing from one culture to another, from one way of life to another, from one religion to another.
Passing over is a shifting of standpoint, a going over to the standpoint of another culture, another way of life, another religion.” (interfaith)

“It is followed by an equal and opposite process we might call ‘coming back,’ coming back with new insight to one’s own culture, one’s own way of life, one’s own religion.”adventure of our time.”  (intrafaith.)

Professor Judith Berling at the Graduate Theological Union also uses this kind of language in Understanding Other Worlds: A Guide for Interreligious Education.
She describes the two poles of the interreligious learning process:

1) understanding another religion faithfully (interfaith)

2) reappropriating Christian tradition in light of new understandings and relationships.(intrafaith)

I love how Dunne ends his explanation: “Passing over and coming back, it seems, is the spiritual adventure of our time.”

I agree! And I hope others do too and will join in the conversation.

Dunne, John, The Way of All the Earth. New York: Macmillan, 1972.
Berling, Judith, Understanding Other Worlds: A Guide for Interreligious Education. Maryknoll, NY: Orbis Books, 2004.