When you talk to the half-wise, twaddle; when you talk to the ignorant, brag; when you talk to the sagacious, look very humble and ask their opinion.
Source: Paul Clifford, 1835.
-- Edward G Bulwer-Lytton, (May 25 1803-1873), English statesman, poet; He is chiefly remembered as a prolific novelist and his skill in anticipating and satisfying changes in public taste.