Anyone can explain further?
In the third book of his work On The Trinity, Richard succeeded in developing an analogy of love that was fully triadic. “God is love” (1 John 4:8): such was his starting-point. Love is the perfection of human nature, the highest reality within our personal experience; and so it is the quality of love that brings us closest to God, expressing – better than anything else that we know – the perfection of the divine nature.
Richard then took a second step in his argument. Self-love, the love of one turned inwards, is not true love. Love signifies self-giving and exchange, and so it cannot be genuinely present unless it is mutual; it presupposes a “thou” as well an an “I.” True love can only exist, in the case, where there is a plurality of persons: “The perfection of one person requires fellowship with another,” wrote Richard. This is the case not only with human beings but likewise with divine being: divine love, as well as human, is fundamentally relational, and is characterized by sharing and communion. The fullness of glory, he affirmed, “requires that a sharer of glory be not lacking.” In God’s case, as in that of human persons, “nothing is more glorious … than to wish to have nothing that you do not wish to share.” If, then, God is love, it is inconceivable that he should be merely one person loving himself. He has to be at least two persons, Father and Son, loving each other.
Next, Richard took a crucial third step in his analysis of God’s relational being. To exist in plentitude, love needs to be not only “mutual” but “shared.” The closed circle of mutual love between two persons still falls short of the perfection of love; in order that such perfection may exist, the two have to share their reciprocal love with a third. “Perfect love casts out fear” (1 John 4:18); love in its perfection is without selfishness or jealousy, without fear of a rival. Where love is perfect, then, the lover not only loves the beloved as a second self, but wishes the beloved to have the further joy of loving a third, jointly with the lover, and of being jointly loved by that third. “The sharing of love cannot exist among any less than three persons. … Shared love is properly said to exist when a third person is loved by two persons harmoniously and in community, and the affection of the two persons is fused into one affection by the flame of love the a third.” In the case of God the Trinity, the “third” with whom the first two, the Father and the Son, share their mutual love is precisely the Holy Spirit, whom Richard termed condilectus, the “co-beloved.”
In this way Richard of St. Victor, in common with the Cappadocians, saw God in terms of interpersonal koinonia or communion. Following Augustine, he started with the relationship between lover (amans) and beloved (quod amatur). But then, instead of making the third member of the Trinity simply the love (amor) that passes between the first two, he treated the Holy Spirit as a fully personal subject, not just “love” but “co-beloved.” Instead of being dyadic, as in Augustine, the relationship affirmed by Richard is genuinely triangular. In Richard’s Triadology, then, there is a movement from self-love to mutual love, and so to shared love: from the love of the one (the Father alone) to the love of the two (Father and Son), and from this to the love of three (Father, Son, and Holy Spirit). There is, according to Richard, no need to go beyond the number three; for, when the circle of the mutual love between lover and beloved is enlarged to include the co-beloved, the pattern of love is complete. In the words of Gregory of Nazianzus (not actually quoted by Richard): “The monad, moving forth into the dyad, came to rest in the triad.”