Dietrich Von Hildebrand

Our belief in the teachings of the Church de fide must be an absolute and unconditional one, but we should not imagine that our fidelity to the Church's theoretical authority is satisfied merely by acceptance of ex cathedra pronouncements.  We must also adhere wholeheartedly to teachings of the Church in matters of morality, even if they are not defined ex cathedra.  The teachings of the encyclical Humanae Vitae, for example, is binding because its content had always been part of the teaching of the Church; in it we are confronted with the theoretical authority of the Church embodied in the tradition of the ordinary Magisterium. It is not a mere practical commandment of the Church, like the commandment to go to church on Sunday.