What are the 4 stages of love according to St. Bernard of Clairvaux?

In his sermon “The Love of God” (also called “On Loving God”), St. Bernard of Clairvaux wrote that love is essential for the knowledge of God. He outlined four stages, or degrees, of love that a person must proceed through for spiritual growth. The four stages in their order of progress are: love of oneself for self’s sake, love of God for self’s sake, love of God for God’s sake, and love of oneself for God’s sake.