Objection 1. It would seem that the knowledge, which is numbered among the gifts, is practical knowledge. For Augustine says (De Trin. xii, 14) that "knowledge is concerned with the actions in which we make use of external things." But the knowledge which is concerned about actions is practical. Therefore the gift of knowledge is practical.
Objection 2. Further, Gregory says (Moral. i, 32): "Knowledge is nought if it hath not its use for piety... and piety is very useless if it lacks the discernment of knowledge." Now it follows from this authority that knowledge directs piety. But this cannot apply to a speculative science. Therefore the gift of knowledge is not speculative but practical.
Objection 3. Further, the gifts of the Holy Ghost are only in the righteous, as stated above (Question 9, Article 5). But speculative knowledge can be also in the unrighteous, according to James 4:17: "To him... who knoweth to do good, and doth it not, to him it is a sin." Therefore the gift of knowledge is not speculative but practical.
On the contrary, Gregory says (Moral. i, 32): "Knowledge on her own day prepares a feast, because she overcomes the fast of ignorance in the mind." Now ignorance is not entirely removed, save by both kinds of knowledge, viz. speculative and practical. Therefore the gift of knowledge is both speculative and practical.
I answer that, As stated above (Question 9, Article 8), the gift of knowledge, like the gift of understanding, is ordained to the certitude of faith. Now faith consists primarily and principally in speculation, in as much as it is founded on the First Truth. But since the First Truth is also the last end for the sake of which our works are done, hence it is that faith extends to works, according to Galatians 5:6: "Faith... worketh by charity."
The consequence is that the gift of knowledge also, primarily and principally indeed, regards speculation, in so far as man knows what he ought to hold by faith; yet, secondarily, it extends to works, since we are directed in our actions by the knowledge of matters of faith, and of conclusions drawn therefrom.
Reply to Objection 1. Augustine is speaking of the gift of knowledge, in so far as it extends to works; for action is ascribed to knowledge, yet not action solely, nor primarily: and in this way it directs piety.
Hence the Reply to the Second Objection is clear.
Reply to Objection 3. As we have already stated (8, 5) about the gift of understanding, not everyone who understands, has the gift of understanding, but only he that understands through a habit of grace: and so we must take note, with regard to the gift of knowledge, that they alone have the gift of knowledge, who judge aright about matters of faith and action, through the grace bestowed on them, so as never to wander from the straight path of justice. This is the knowledge of holy things, according to Wisdom 10:10: "She conducted the just... through the right ways... and gave him the knowledge of holy things."
Source: Summa Theologica (New Advent)