moral absolutism
The opposite of moral relativism, moral absolutism refers to belief in absolute moral grounded in God. Note that moral absolutism is both absolute and not absolute. As the magisterium of the Catholic church discerns more of God's truth and we understand His will better, they adapt their absolute definition of morals to reflect the newfound truth. However, this truth has been there all along and we were just doing it the wrong way previously, so it is the absolute truth (I think, but I'm not sure. Too much Catholic politics).
The Catholic church claims to have always followed a principle of moral absolutism. In the middle ages, it was discerned that indulgences were OKAY. After Martin Luther did the East–West Schism, the Catholic church found itself with less power and affluence due to its reduced size, so it went back to the Bible and reinterpreted it to mean that indulgences are NOT OKAY.