What, of course, is designated by this book if not Holy Scripture, which only our Redeemer opened?
By becoming man, dying, rising, and ascending, He opened all the mysteries that were in it.
No one in heaven was worthy, because not even an angel could do this.
No one on earth was worthy, because not even a man living in the body could do this.
No one under the earth was found worthy, because even souls freed from the body could not reveal to us the secrets of the holy utterance apart from the Lord.
Therefore, since no one found under the earth is considered worthy to explain the book, I do not see what should hinder belief that Hades exists under the earth.