Who said "He who knows not himself knows nothing."?

This quote is attributed to Don Quixote.

He who knows not himself knows nothing. - Don Quixote

"He who knows not himself knows nothing."

Don Quixote

Character in Don Quixote

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"The Knight of the Sorrowful Countenance"

"I know who I am, and who I may be, if I choose."

"Facts are the enemy of truth."

"The pen is mightier than the sword."