A learned teacher is not necessary the wisest

"Magis magnos clericos non sunt magis magnos sapientes" [them most biggest clerks ain't the most wisest].

Yet how it can happen that a soul enriched by so much knowledge should not be more alert and alive, or that a grosser, commonplace spirit can without moral improvement lodge within itself the reasonings and judgements of the most excellent minds which the world has ever produced: that still leaves me wondering.

Michel de Montaigne - Complete Essays (I, 25)