Who said “To teach is to learn twice.”?

“You teach best what you most need to learn.”

“Nothing that is worth knowing can be taught.”

“Who dares to teach must never cease to learn.”

“A professor is one who talks in someone else's sleep.”

“Teaching is not a lost art, but the regard for it is a lost tradition.”

“Imagination is the eye of the soul.”

“Ask the young. They know everything.”

“Tenderness is the repose of passion.”

“Logic works, metaphysics contemplates.”

“A part of kindness consists in loving people more than they deserve.”

“The aim of an argument or discussion should not be victory, but progress.”