Inspired by Christ's prayer for unity in the Gospel of John and Saint John Paul II's encyclical Ut Unum Sint, Kreeft demonstrates that Christian reunification is possible. While he acknowledges that there are still significant differences between Catholics and Protestants, he emphasizes that they agree on the single most important issue: justification.

The style of this book is modeled on Pascal, Solomon, and Jesus: short answers and single points to ponder rather than long strings of argument. The writing is direct, simple, and confrontational, but vertically rather than horizontally by "directing arrows not against each other (Protestant or Catholic) but against our own hearts and minds and wills."

The purpose of this book, writes Kreeft, is to be "like an Australian sheepdog, herding and hectoring Christ's separated sheep back to His face. For that is the only way they can ever return back to each other."