What is the first business of one who studies philosophy? To part with self-conceit. For it is impossible for any one to begin to learn what he thinks that he already knows.
Epictetus (c.55-c.135) Greek (Phrygian) Stoic philosopher
The Discourses, ch. 17, “How To Apply General Principles to Particular Cases” (c. AD 101-108)
Alt. trans.: "It is impossible for a man to begin to learn what he thinks he knows." [tr. Long (1890)]