The Holy Spirit in the Church
"And God, the true God, is the God we see in Jesus of Nazareth, Israel's Messiah, the world's true Lord, and in the Spirit which he sends. The earliest Christians spoke of God and Jesus in the same breath - and, of course, the word 'breath' is pneuma, the same word as 'Spirit' - and, so to speak, on the same side of the equation. Paul wrote that if you want to know who the real God is, as opposed to the non-gods of paganism, you must think in terms of the God who, to fulfil his age-old plan to rescue the world, sent first his Son and then the Spirit of his Son (Galatians 4.4-7). You either have the Trinity or you slide back into paganism."