With these words slamming the door on Catholics’use of modern contraceptives, Pope Paul VI cleaved the Catholic church into irreconcilable factions 40 years ago. The majority, unable to reconcile the rigid encyclical with their need for an updated sexual ethic based less on the biological function of reproduction and more on the evolving nature of companionate sexual relationships, embraced individual conscience in matters of contraception and, increasingly, in other issues. Meanwhile, a minority sought desperately to reassert the principle of absolute obedience to the hierarchy, particularly on matters of sexuality, becoming more entrenched with each passing decade. Even 40 years later, the wounds have not healed. For many Catholics, both clergy and lay, their relationship with the church would never be the same. And the church itself would be radically altered, unable to move forward; forever defending a teaching that was judged indefensible 40 years ago and has only become more so with the passage of time and the arrival of new issues related to contraception, such as preventing the spread of HIV and AIDS. How did this most controversial of the Catholic hierarchy’s teachings come about?Why did the hierarchy fly in the face of Catholics’evolving and very real need for an updated ethic regarding human sexuality? And, most importantly, what has the impact of this disputed teaching been on the Catholic church, and the world at large?