"Nequicquam sapit qui sibi non sapit" is from Erasmus' Adagia. The translations I have found on the internet typically convey a meaning along the lines "He knows in vain who does not make use / profit from what he knows."

"Nequicquam sapit qui sibi non sapit" is from Erasmus' Adagia. The translations I have found on the internet typically convey a meaning along the lines "He knows in vain who does not make use / profit from what he knows."