There are many points which the Church leaves to the dis cussion of theologians, in that there is no absolute certainty about them. As the eminent Cardinal Newman remarked, such controversies do not disrupt the Church's unity; rather they contribute greatly to a deeper and better understanding of her dogmas. These very differences shed in effect a new light on the Church's teaching, and pave and fortify the way to the attainment of unity."

From the Encyclical Letter Ad Petri Cathedram of Pope John.