The early Christians were confronted with a number of realities which were theologically perplexing but nevertheless integral elements of their shared faith. They were monotheists who believed that God was one. Yet they offered divine worship to Jesus Christ as Lord, risen from the dead. And in their communal worship they experienced personally the Holy Spirit as a sovereign, divine person lifting their hearts in praise, empowering them with spiritual gifts and transforming their lives.
Christians did not at this early stage seek to explain this set of paradoxes. They did, however, in their greetings and benedictions regularly refer to Father, Son and Spirit as the shared authors of human salvation. The pattern of the Trinitarian affirmation in the passage above is not unusual.
Chosen by the Father
Sanctified by the Spirit
Saved by the blood of Jesus
In expressions such as these the various elements of salvation are attributed to the three divine persons not as absolute distinctions but as appropriate ones. The Father through his love and eternal determination is recognised as the ground of our salvation, or as we might say, the formal cause. Jesus Christ by way of his redemptive life, death and resurrection, is often spoken of as the one who purchased us for God, the material cause of our salvation. The Holy Spirit as the agent of our new birth and spiritual transformation, protecting us for a salvation to be finally revealed is what we might describe as the efficient cause. In the post-apostolic period the Church developed a more compact Trinitarian master-narrative. It became common to speak of the believer coming to the Father, through the Son, by the power of the Spirit. The formulations of later Trinitarian discussion were further abstracted from the story of salvation, but the intention was the same, that is, to speak of the one God in a way which affirms the divinity of Father, Son and Spirit and recognises a distinction between their persons:
We worship one God in trinity
and the Trinity in unity,
neither confusing the persons
nor dividing the divine being.
(Athanasian Creed)