Omit “that which is.” “Wisdom” is the subject of both clauses. She is “made known,” that is, by the very force of contrast, in the midst of fools; …

But that which is in the midst of fools is made known.— “Wisdom” is the subject of this as of the former half of the vers…

Wisdom rests in the heart of him that has understanding, &c.] It is in his heart, as the treasury where it is laid up, an…

Wisdom possesses the heart, and thus regulates the affections and tempers.