Mere Marriage explains how Pope John Paul's Theology of the Body gave consistency and form to a Christian doctrine of sexual difference, illuminated human dignity and all Christian Mysteries. It raised the bar on dissent from the doctrine of Humanae Vitae, it presents an authentic Christian humanism, and it seizes the high ground in opposition to secular attacks on marriage, human dignity, freedom and equality. Pope Saint John Paul took the advice of his friend Henri Cardinal de Lubac, S. J.: "When something so fundamental [viz. as sexual difference] is called into question you have to get down to its roots...the whole matter has to be studied from a new viewpoint. Fundamentally, what you feel is a need to see straight."