Didn’t Chesterton compare an open mind with an open mouth?
Indeed, he did. But only twice.
“An open mind is really a mark of foolishness, like an open mouth. Mouths and minds were made to shut; they were made to open only in order to shut.” (Illustrated London News. October 10, 1908)
“The object of opening the mind, as of opening the mouth, is to shut it again on something solid.” (Autobiography)