A man whose intellect has been formed by the knowledge that comes by dint of the virtues through the divine Spirit is said to experience divine things; for he has acquired such knowledge not by nature, thanks simply to his existence, but by grace, thanks to his participation in it.  When a man has not received knowledge by grace, even though he calls a particular thing spiritual, he does not know its true character from experience.  For mere learning does not produce a state of spiritual knowledge.

St. Maximus the Confessor