Thus, with Urban ruling from Rome and Clement from Avignon, the murky chapter in papal history called the Great Schism of the papacy begins. It lasted for thirty-nine years. Each pope had his own College of Cardinals, thereby insuring the papal succession of its own choice. Each pope claimed to be the true Vicar of Christ, with the power to excommunicate those who did not acknowledge him.
As the Roman church had for centuries, Aquinas held that it is a true sacrifice, continuing that of Christ on the cross, and predisposing God to be gracious to those for whom it is offered. In the Supper the essence of the bread and wine are changed miraculously into the actual body and blood of Christ while the exterior remains unchanged, a doctrine known as transubstantiation—of which Thomas gave the classic presentation.
Furthermore, by his love, the loving person enables the beloved person to actualize these potentialities. By making him aware of what he can be and of what he should become, he makes these potentialities come true.
I thought he was so good he'd change me, but no one ever really changes. We can be different for a while but we'll never change what is true in our bones and brains.