Tracking it down

I read a snappier version of this in You Call this Living and thought I should see where it came from.

On an official visit to Paris in 1963 at the death of Jean Cocteau, Jaroslow Iwaskiewicz, President of the Union of Writers and Dramatic Authors, and author of the novel _Mother Joan of the Angels_, was asked by Adrezej Moosman, directory of Slavic language broadcasts: "Are you a catholic?" Iwaskiewicz answered in a detached tone, "Yes, I am a believer but not a practicing Catholic." His companion retorted, "And doesn't that prevent you from having an important official job in a communist country?" The retort was a witty: "That's different, in that case I am practicing, but not a believer."

Found here