The Seraphic Soul
Everyone is called to holiness and in that holiness is able to obtain complete happiness. But God always chooses some for a special mission of holiness, a higher form of holiness. These souls could be called “Seraphic Souls.” The classic example is to compare two glasses of water. One is large and one is small. They are both filled to the brim so they are both full. But one contains more water. So it is with holiness. Some are given a special calling to reach a greater height. All people are to be “full” of the Holy Spirit and, thus, obtain perfect happiness. But some are invited higher in a unique way. This is similar to the Nine Choirs of Angels. The Seraphim are of the highest order and have as their sole purpose the worship and adoration of God. The Guardian Angels are of the lowest order and have as their primary duty the service of man. Each celestial being is perfectly happy and rejoices in the unique calling of each (See Diary #1556).
Devotion to the souls in Purgatory contains in itself all the works of mercy, which supernaturalized by a spirit of faith, should merit us Heaven. de Sales