The origin of the Holy Spirit from the Father alone as Principle of the whole Trinity is called ' by Greek tradition, following the Cappadocian Fathers. St. Gregory of Nazianzus, the Theologian, in fact, characterizes the Spirit's relationship of origin from the Father by the proper term ekporeusis, distinguishing it from that of procession (to proienai) which the Spirit has in common with the Son. "The Spirit is truly the Spirit proceeding (proion) from the Father, not by filiation, for it is not by generation, but by ekporeusis." Even for Cyril, the term ' as distinct from the term "proceed" (proienai), can only characterize a relationship of origin to the principle without principle of the Trinity: the Father.