The lustre of diamonds is invigorated by the interposition of darker bodies; the lights of a picture are created by the shades; the highest pleasure which nature has indulged to sensitive perception is that of rest after fatigue.
Source:
-- Samuel Johnson, (Sep 18 1709-1784), English lexicographer, critic; He was remembered for writing the first critique of Shakespeare, 1765 and Dictionary of the English Language, 1755.