The Most Essential Article of the Christian Faith

The early Apostolics loved the Trinity and they loved the doctrine of the Trinity. They even said it was 'the most essential article of the Christian faith' and that ‘it is absolutely necessary to believe in the Trinity in the Divine Essence before we can fully grasp and appreciate the other doctrines of our faith.' Just look at where they put the Trinity in the Tenets. Unlike most other evangelical statements of faith (but like the ancient creeds), the Trinity stands in first place. (Most evangelical statements of faith start with the authority of Scripture, which doesn't make it into the Tenets until number 8, when they have moved on to consider the Church). And for the early Apostolics, the Trinity wasn't just a doctrine to be checked off the list to ensure you were 'sound', but rather it was of vital importance to all of the Christian faith and the Christian life.

The two quotes at the beginning both come from Thomas Rees, one of the early Welsh apostles in the Apostolic Church. Pastor Rees also emphasised how only the doctrine of the Trinity could make sense of a God who is love:

For if God were not a Trinity in unity, on whom could His love have been lavished, when there was no-one eternally existent but only Himself as a solitary unit? … Therefore to deny the distinction of the Father, Son and Holy Ghost in the eternal Being of God is to make the love of God dependent on things created, and that would contradict the self-existence and the self-sufficiency of God. Origen, one of the early Christian fathers, argues like this: 'If God had ever existed in simple unity and solitary grandeur apart from some object upon which from all eternity to pour forth His love, His love, His Fatherhood and His very omnipotence would have been added in time, and there would have been a time when He was not perfect.' … But we are not left in the dark as to upon whom the Father lavished His love. For in John xvii : 24 we find Jesus declaring: ‘Father … Thou lovedst me before the foundation of the world.’
(Thomas Rees, The Unity of the Godhead and the Trinity of the Persons Therein)

And, by the way, it's not just that the Trinity's very important - it's essential. As Thomas Rees points out, without the doctrine of the Trinity, 'the whole scheme of redemption collapses, and with it all the essential and vital truths which we hold as an Apostolic Church.' The doctrine of the Trinity isn't 'deep teaching' for mature Christians; the doctrine of the Trinity is the Christian faith and the foundation of the Christian life.