God, in His wisdom, decided that each angel would determine its degree of glory for eternity by its response to a divine test. Each angel determined its degree of happiness by the degree of generosity, love, constancy, and other virtues it displayed in the test. A spirit can grow in its faith and in its generosity toward God before it sees Him. But once admitted to the Beatific Vision, no further growth is possible—there can no longer be growth in faith where there is vision. Above all, the period of testing offered the angels the opportunity to grow in the theological virtues, and some angels would grow more in the virtue of perseverance, others in humility, others in petition, etc.