"A little knowledge is a dangerous thing"

"A little learning is a dangerous thing; drink deep, or taste not the Pierian spring:

there shallow draughts intoxicate the brain, and drinking largely sobers us again."

Alexander Pope (1688 - 1744) in An Essay on Criticism, 1709

(Greek Mythology: The Pierian Spring, in Macedonia, sacred to the Muses as a source of inspiration)

One possible meaning, because everything is open to interpretation:

A small amount of knowledge may lead people to believe that they know and are better at something than they really are.