Ronald A. Knox (1888-1957), Enthusiasm: A Chapter in the History of Religion with Special Reference to the XVII and XVIII Centuries
(1950; rpt. New York: Oxford University Press, 1961), p. 196:
A kind of intellectual inbreeding was the inevitable result of shutting up so many like-minded people in the same enclosure. An indefinable spirit of 'Here's tae us, and wha's like us?' dominates their interminable biographies of one another.
Id., pp. 229-230:
The enthusiast wants to see results; he is not content to let the wheat and the tares grow side by side until the harvest. It must be made possible somehow, even in this world, to draw a line between the sheep and the goats. Thus a little group of devout souls isolates itself from the rest of society, to form a nucleus for the New Jerusalem; and in doing so it loses touch with the currents of thought that flow outside, grows partisan in its attitude, sterile of new ideas.