For my money you can’t do much better than this in talking about the Christian doctrine of God. This is long, but I couldn’t bear to cut the quote off. It’s just too good:

Jesus is God’s word, God’s idea of God, how God understands himself. He is how-God-understands-himself become a part of our human history, become human, become the first really thoroughly human part of our history—and therefore, of course, the one hated, despised, and destroyed by the rest of us, who wouldn’t mind being divine by are very frightened of being human.

In Jesus, says the Christian, we do not understand God but we can watch God understanding himself. God’s understanding of God is that he throws himself away in love, that he keeps nothing back for himself. God’s understanding of God is that his a love that unconditionally accepts, that always lets other be, even if what they want is to be his murderers. God’s understanding of God is that he is not a special person with a special kind of message, with a special way of living to which he wants people to conform. God’s understanding of God could not appear to us as someone who wants to found a new and better religion, or recommend a special new discipline or way of life—a religious code laid upon us for all time because it is from God. God’s understanding of God is that he just says: ‘Yes, be; be human, but be really human; be human if it kills yous—and it will.’ The Law of God is a non-law; it has no special regulations. The Word just says: ‘I accept you as human beings; what a pity you can only like yourselves if you pretend to be super-humans or gods.’ God could never understand himself as one of the gods; only as one of the human race.

Let us be absurd for a minute and try to imagine what it means for God to understand himself. I don’t mean try to think or understand it (of course we cannot do that). But let us try to imagine understanding that limitless abyss of life and liveliness, that permanent explosion of vivacity and awareness and sparkling intelligence and, of course, humour. And remember that in understanding himself God will thereby be understanding all that he has done and is doing, all that he holds in being, every blade of grass and every passing thought in your mind. The concept he has of himself in all this is his Word. This is what is made flesh and dwells among us in the human suffering and dying Christ.

And in contemplating his life in this Word, in this concept, in contemplating all he is and does, God has surely a huge unfathomable joy and immense excitement in all the life that is his and all the life he has brought into being. God takes immensely more joy in one little beetle walking across a leaf than you can take in everything good and delightful and beautiful in your whole life put together. If he gets that pleasure from one beetle he has made, think then what joy he takes in being God. This limitless joy is what we call the Holy Spirit.

To be able, through faith, to share in Christ, in God’s understanding of himself, to be in Christ, is to be filled ourselves also with this joy, this Holy Spirit. It is a joy so vast that we can only faintly sometimes it as our elation and joy—just as our sharing in God’s self-understanding hardly at all seems to us an understanding, a being enlightened. We have a life in us, an understanding and a joy in us, that is too great for us to comprehend. Quite often it has to show itself as what seems its opposite, as darkness and suffering. The Word of God is Christ crucified. But it is God’s way and the truth of God and the life and joy of God. And this is in us because we have faith. We have been prepared to go into the dark with Christ, to die with Christ. And we know that this means we live in Christ. And that life, the divine understanding and joy that is in us, will one day soon show itself in us for what it truly is. And we shall live with the Father, through the understanding which is the Word made flesh, in the joy which is the Holy Spirit for eternity.

~ Herbert McCabe, God Still Matters, 104-6.