St. Francis de Sales: “There is no other true knowledge given but that which is given by the Holy Ghost.”

Sermo 23 in die Pentecostes alter, circa medium
There is no other true knowledge given but that which is given by the Holy Ghost. And this is granted to the humble only. Have we not known great theologians who spake marvellously of the virtues but did not practice them? Have we not seen, on the contrary, many women who did not know how to discourse on the virtues, practice the works of virtue worthily? The Holy Spirit hath made these wise because they had fear of the Lord, piety and humility.

- Homily of St. Francis de Sales, Bishop