One of the great mysteries, if not THE great mystery of the Christian faith is that there is one God, yet three “persons” in that one God. This is the idea of the Trinity. Like we read in John 1:1 In the beginning was the Word, and the Word was with God and the Word was God. Then in John 1:14 we read that this same Word who was at the same time with God and was God, became flesh and lived for a while among us. We beheld his glory–the glory of the one and only Son of God. The idea that God is one yet three is a logical conundrum, yet this is one of the central claims of Christianity. The Father is God, the Son is God and the Holy Spirit is God. Yet the Father is not the Son, the Son is not the Holy Spirit, and the Holy Spirit is not the Father. This is the clear an unmistakeable claim of Jesus and of the New Testament Scripture. It is a deep, and seemingly not even “logical” truth of Scripture. Jesus said in John 8 “Before Abraham was born, I AM. John 8:58. We read in Colossians 2:9 that in Jesus the fullness of deity dwelt in bodily form, yet, Jesus prayed to the Father and Jesus obeyed the Father (John 14). This is one of the great mysteries of Christianity which theologians have tried, in vain, to explain using human logic. Yet, Jesus, who walked on water, calmed a great storm, turned water to wine, made bread and fish for ten thousand, who raised Lazarus and Jarius’ daughter from the dead and who, himself, was resurrected from the dead after three days, tells us that he is God, but he clearly is not the Father, and the Father sent the Holy Spirit as well. Again, this is the mystery which we label as the Trinity.
Your second question is one which has been asked by many people for sure. Actually, for all we know Jesus did write personal letters. He certainly was literate. He wrote on the ground in John 8:1-15. So, to say that he wrote nothing is almost certainly not true. However, it appears that it was God’s will that nothing he wrote has come down to us. If you think about it, 99.9% (of course, I am making this number up. Please forgive me) of people who lived back then, even the ones who could write, have left nothing behind for us to read. I am not saying it is not surprising we have nothing written by Jesus. I say that it is at least a little bit surprising that nothing he wrote has come down to us. I guess we will just have to continue wondering why nothing he wrote was written for posterity, and that all God communicated to us of his life was recorded by those who knew him.
John Oakes