“The heresy of (religious ethnocentrism): thinking oneself a completely self-sufficient unit and asserting this imaginary ‘unity against all others. The affirmation of the self (or group) as simply ‘not the other.’ But when you seek to affirm your unity by denying that you have anything to do with anyone else, by negating everyone else in the universe until you come down to you: what is there left to affirm?
The true way is just the opposite: the more I am able to affirm others, to say ‘yes’ to them in myself, by discovering them in myself and myself in them, the more real I am. I am fully real if my heart says ‘yes’ to everyone.
I will be a better Catholic, not if I can refute every shade of Protestantism, but if I can affirm the truth in it and still go further. So, too, with the Muslims, the Hindus, the Buddhists, etc. This does not mean syncretism, indifferentism, the vapid and careless friendliness that accepts everything by thinking of nothing. There is much that one cannot ‘affirm’ and ‘accept,’ but first one must say ‘yes’ where one really can.
If I affirm myself as a Catholic merely by denying all that is Muslim, Jewish, Protestant, Hindu, Buddhist, etc., in the end I will find there is not much left for me to affirm as a Catholic, and certainly no breath of the Spirit with which to affirm it.”
--Thomas Merton in Conjectures of a Guilty Bystander