he who kisses, the Son he who is kissed, then it cannot be wrong to see in the kiss the Holy Spirit, for he is the imperturbable peace of the Father and the Son, their unshakable bond, their undivided love, their indivisible unity. – St. Bernard of Clairvaux, in Sermon 8, Sermons on the Song of Songs The devotion of themselves to each other in the Spirit by the Father and the Son has content. Not only does the procession of the Spirit from the Father to the Son and from the Son to the Father express their mutual love, as they breathe after each other, but also it gives each to the other. In the procession of the Spirit from the Father, the Father gives himself to the Son; in the procession of the Spirit from the Son to the Father, and in this use of the word "procession" from the Son is meant the sending of the Holy Spirit as the Son teaches that the Holy Spirit proceeds from the Father, the Son gives himself to the Father in prayer, for the procession of the Spirit, like the begetting of the Son, is the going forth of the being of the Father to the Son and the going forth of the being of the Son to the Father as the Holy Spirit. The property of divine grace in the Trinitarian mission is distinct for each person or hypostase of the Holy Trinity yet united, communing, indwelling, in Trinitarian love. All is God's gift from the Father, through the Son's Incarnation and in the gift of the Holy Spirit. This relational co-inherence is often represented as Borromean rings or the Scutum Fidei. The tombstone of the twentieth-century Swiss mystic and Catholic convert Dr. Adrienne von Speyr features a three-dimensional monolithic stone carving resembling the bas-relief two-dimensional carved eternal-knot symbol of Norse mythology, the valknut, used to eulogize legendary valor surpassing human understanding. Social trinitarianism Church Fathers The relationship between the Father, Son and Holy Spirit was not explicitly expressed in the writings of Ante-Nicene Fathers exactly as it would later be defined during the First Council of Nicaea (325) and the First Council of Constantinople (381), namely as one substance (ousia) and three persons (hypostaseis). A hermeneutic of the one-in-three principle slowly approached the synthesis understood today as perichoresis. Human body as icon of the communio personarum The crucial