Sign of Insanity?

"He was talking very excitedly to me," said the Vicar, "about some apparatus for warming a church in Worthing and about the Apostolic Claims of the Church in Abyssinia. I confess I could not follow him clearly. He seems deeply interested in Church matters. Are you quite sure he is right in the head? I have noticed again and again since I have been in the Church that lay interest in ecclesiastical matters is often a prelude to insanity."

Decline and Fall by Evelyn Waugh (1928).