Al-Khalil b. Ahmad remarked: ‘There are four types of people:
(1) One who knows and knows he knows; he is learned, so follow him!
(2) One who knows and knows not that he knows; he is asleep, so wake him!
(3) One who knows not and knows he knows not; he seeks to learn, so teach him!
(4) One who knows not and knows not that he knows not; he is a fool, so shun him!’
(Cited in Ibn ‘Abd al-Barr, Jami‘ Bayan al-‘Ilm (Saudi Arabia: Dar Ibn al-Jawzi, 1994), no.1538.)