3 Now it ought to be known that the holy apostles, in preaching the faith of Christ, delivered themselves with the utmost clearness on certain points which they believed to be necessary to every one, even to those who seemed somewhat dull in the investigation of divine knowledge; leaving, however, the grounds of their statements to be examined into by those who should deserve the excellent gifts of the Spirit, and who, especially by means of the Holy Spirit Himself, should obtain the gift of language, of wisdom, and of knowledge: while on other subjects they merely stated the fact that things were so, keeping silence as to the manner or origin of their existence; clearly in order that the more zealous of their successors, who should be lovers of wisdom, might have a subject of exercise on which to display the fruit of their talents—those persons, I mean, who should prepare themselves to be fit and worthy receivers of wisdom.
Source: De Principiis (New Advent)