Philip Dormer Stanhope, 4th earl of Chesterfield, letter to Philip Stanhope, his natural son, November 24, 1747.—The Letters of Philip Dormer Stanhope, 4th Earl of Chesterfield, vol. 3, p. 1057 (1932). The second part of the sentence quotes the Bible, Matthew 15:14. In a later letter to his son, January 15, 1753, Lord Chesterfield remarked that "Young men are as apt to think themselves wise enough, as drunken men are to think themselves sober enough".—Letters, vol. 5, p. 1994–95https://en.wikiquote.org/wiki/Youth