Respectfully Quoted: A Dictionary of Quotations. 1989.
George Santayana (18631952)
Every actual animal is somewhat dull and somewhat mad. He will at times miss his signals and stare vacantly when he might well act, while at other times he will run off into convulsions and raise a dust in his own brain to no purpose. These imperfections are so human that we should hardly recognise ourselves if we could shake them off altogether. Not to retain any dulness would mean to possess untiring attention and universal interests, thus realising the boast about deeming nothing human alien to us; while to be absolutely without folly would involve perfect self-knowledge and self-control. The intelligent man known to history flourishes within a dullard and holds a lunatic in leash. He is encased in a protective shell of ignorance and insensibility which keeps him from being exhausted and confused by this too complicated world; but that integument blinds him at the same time to many of his nearest and highest interests. He is amused by the antics of the brute dreaming within his breast; he gloats on his passionate reveries, an amusement which sometimes costs him very dear. Thus the best human intelligence is still decidely barbarous; it fights in heavy armour and keeps a fool at court.
GEORGE SANTAYANA, The Life of Reason, vol. 1, chapter 2, pp. 5051 (1905).