An Open Mind

Northrop Frye, The Great Code: The Bible and Literature (New York: Harcourt Brace Jovanovich, 1983), p. 44:

[A]n open mind, to be sure, should be open at both ends, like the foodpipe, and have a capacity for excretion as well as intake.

Update: Thanks to Dave Lull for drawing my attention to a different view, that of J.V. Cunningham, Epigrams: A Journal, #30:

This Humanist whom no beliefs constrained
Grew so broad-minded he was scatter-brained.