“When asked what learning was the most necessary, he said, "Not to unlearn what you have learned."”

“Antisthenes … was asked on one occasion what learning was the most necessary, and he replied, "To unlearn one's bad habits."”

“The most necessary learning is that which unlearns evil. ”

“The most useful piece of learning for the uses of life is to unlearn what is untrue.”

“Aristippus being asked what were the most necessary things for well-born boys to learn, said, "Those things which they will put in practice when they become men."”

“Half of wisdom is learning what to unlearn.”

“When one asked him what boys should learn, "That," said he, "which they shall use when men."”

“The mind unlearns with difficulty what it has long learned.”

“You must acquire the best knowledge first, and without delay; it is the height of madness to learn what you will later have to unlearn.”

“The learned are said to have seeing eyes;
The unlearned have only two sores on their faces.”