Imagine a set of people all living in the same building. Half of them think it is a hotel, the other half think it is a prison. Those who think it a hotel might regard it as quite intolerable, and those who thought it was a prison might decide that it was really surprisingly comfortable. So that what seems the ugly doctrine is one that comforts and strengthens you in the end. The people who try to hold an optimistic view of this world would become pessimists: the people who hold a pretty stern view of it become optimistic.
