The Church is larger and more alive than we think. Among her members are the living and the deceased (whether they are still undergoing a process of purification or are already in the glory of God), individuals known and unknown, great saints and inconspicuous persons. We can help one another even beyond the grave. We can call on our patrons and favorite saints, but also our departed relatives and friends whom we believe are already with God. Conversely, by our intercessory prayer, we can come to the aid of our dear departed who are still undergoing purification. Whatever the individual does or suffers in and for Christ benefits all. Conversely, this unfortunately means also that every sin harms the communion.
-YouCat, # 146