I have been fairly criticised for not saying enough positive things about what I DO believe, as opposed to pointing out things that I DON'T believe. I think there is a real need for the latter, as so often Christianity is misrepresented or misunderstood, including by (perhaps especially by) Christians themselves, but it can become irritating on its own. So here is, hopefully, a more positive line of thought.
1. Christianity begins with Jesus, and a response to him. It means accepting his vision as determinative, and his authority as absolute. The gospel is: "Jesus is Lord", the rest is detail.
2. That means, necessarily, taking on board his language and attitudes. It means talking about the Kingdom and the Father and the Spirit and Abundant Life.
3. This language therefore does not begin in abstract speculation, but in an embodied existence.
4. This language is, therefore, vulnerable to historical criticism. There are some historical claims which, if shown to be true, would invalidate Christianity, eg that Jesus was violently abusive, or, that the crucifixion was a sham.
5. This language evolves over time.
6. One of the earliest and most important evolutions was to see Jesus as not just the Messiah, the Christ, but as the 'Word Made Flesh', the purpose of existence expressed in human form. This can be seen in John's gospel - so it is an evolution that took place whilst Jesus was still within living memory.
7. This evolution, that Jesus is the Word Made Flesh, is the heartbeat of my faith, the fixed core around which everything else rotates. I believe that in the life, death and resurrection of Jesus Christ the full meaning of human life and purpose is revealed to us. I believe that Jesus Christ is the way, the truth and the life.
8. I don't believe that this purpose is something that can be rationally proven. I think that there are irrational criticisms of it, which can be overcome, but I don't see becoming a Christian as something which can be driven purely be reason. To become a Christian involves falling in love with Jesus, which is no more subject to rational control than any other falling in love.
9. Of course, you can't fall in love with Jesus unless you know him - hence the importance of the gospels, and historical study of the gospels. To love him is to obey him; it is to love one another as he loved us; it is to become a disciple and to be disciplined in obedience to him.
10. Jesus gathered around himself a group of disciples - both men and women - which later became codified as 'the twelve'. These disciples, as a result of what happened to them, most especially what happened to them at the resurrection, became infused with a completely different way of understanding the world. These disciples called this infusion 'the Holy Spirit' and it enabled them to withstand torture and torments with humility, perseverance, gentleness and grace, such that within a few hundred years this ragtag group of semi-literate peasants had converted all the known world to their faith.
11. At the heart of this faith is relationship - not simply the relationships within the group, or between the group and their God, but the claim that God in himself is relational. This was another evolution of language, this time called 'The Trinity'.
12. What the Trinity expresses is that our human existence is first of all dependent - that we are creatures. Life does not begin with us; it may flow through us, more or less abundantly, but we are not the origin. Consequently our fundamental attitude to our existence is best expressed as thanksgiving. This element of the Trinity is called 'the Father'. Secondly, the Trinity expresses that our purpose as creatures has been revealed to us by the one man Jesus of Nazareth (see above), this is 'the Son'. Thirdly, the Trinity says that the relationship of intimacy between Father and Son, the Holy Spirit, is itself able to be shared in by the faithful. The goal of Christian life is a full and ecstatic absorption into the life of the Trinity.
13. This sharing in the life of the Trinity is a mystery, it is mystical, it is beyond words. Words point to it as fingers pointing to the moon. We cannot capture it in definitions; indeed, the desire to capture it in words is itself a sign of spiritual ill-health, so, one of the comparatively early developments of the language of Christianity was a refinement of the Jewish notion of idolatry, and the application of that notion to the faith journey. This is known as the mystical tradition, which, roughly speaking, runs in its classical form from Denys through to St John of the Cross. This is the via negativa. Everything said about God has to be negated, not in order that nothing is said, but in order that we do not get trapped on a particular rung of the ladder of ascent.
14. The via negativa is theologically mainstream and orthodox. Unfortunately, most especially in Protestant cultures, the insights of the via negativa have been systematically undermined and denied, and aspects of the Western theological cul-de-sac have hardened into dogma. Virtually all atheist criticism of Christianity that I am aware of takes this late-Western-Protestant derivative of orthodoxy to be Christianity as such. Most of their criticisms of it are good ones - it's just that they don't touch the historical mainstream of the faith.
15. It's all about Jesus, and it remains all about Jesus, and it is more relevant than ever.