Saint Symeon the New Theologian’s theology of the Holy Spirit is presented in close connection with the Father and the Son, emphasising the unity and inseparability of the Persons of the Holy Trinity. Through images such as the key in Catechesis 33, the wine in Catechesis 23 and the divine seed, Saint Symeon demonstrates that the grace of the Holy Spirit is essential for purification, deification and the conscious perception of the divine presence in the human soul.