=Profane writings should be read that they may not be unknown.=
Some we read (o) that we may not neglect (a) them; we read that we may not be ignorant of them; we read not that we may embrace them but that we may reject them.(b)
So Jerome on the Epistle to Titus:
=Grammar should be read in order that through it the Sacred
Scriptures may be understood.=
If anyone[V] has learned grammar or dialectics in order to have the ability to speak correctly and to discriminate between the true and the false, we do not blame them. Geometry (c) and Arithmetic and Music contain truth in their own range of knowledge, but that knowledge is not the knowledge of piety. The knowledge of piety is,—to know the law, to understand the prophets, to believe the Gospel, (and) not to be ignorant of the Apostles. Moreover the teaching of the grammarians can contribute to life, provided it has been applied to its higher uses.
Idem:
=From the example of Daniel it is established that it is not a sin to be learned in profane literature.=[W]
(n) Whence Saint Gregory in his LXXXVI Division, and in many places.
(o) This entire section should be read with regard to profane knowledge according to Jerome, and the threefold reason why it should be acquired is shown: namely that it be not neglected, that it be not unknown, that it may be refuted[X]. So we read some, as the Old and New Testament, that we may not neglect them. Some we read (as the Arts) that we may not be ignorant of them. Some, as the writings of the heretics, that we may refute them. Some (we read) that they be not neglected, as the Old Testament.
(a) For although of no use yet knowledge of them is necessary, as in dist. VII. cap. ult.