Against Christianity (Notes 1)

Part 1 - Against Christianity 
Peter Leithart's first section has 23 points to it rather than chapter divisions. This summary will work through it in in chunks.

1. The Bible never mentions Christianity but speaks of Christians and the Church. Christianity is gnostic. 
2. Christianity is the heresy of heresies and underlying cause of the weakness, lethargy, sickness and failure of the modern church. 
3. In itself the linguistic fact of point 1 has little significance. The Bible never uses the word trinity either. The issue is the concept, and 'Christianity' is often used to refer to a set of doctrines or a system of ideas [and is contrasted to the teachings of Judaism, Buddhism, Hinduism or Islam]. But the Bible never speaks of such beliefs except as all-embracing confessions of God's people. No 'belief system' can be isolated from the church and put in the lab for analysis. And the church is not a people committed to common ideas, but is a people committed to a whole stance of life. The Bible in short is not an ideological tract and does not teach an ideology. 
Sometimes 'Christianity' is used to embrace not only beliefs, but the practices of Christian people and the Church. This is better - but not if this is conceived as being a 'religious' layer added onto human life. Being a Christian is not simply a matter of installing a new 'religious' program into an existing operating system - it is the installation of a new operating system. And this goes for church too, for church is not another layer on social life, but is rather, a new way of living before God and of being human together. 
What Jesus and the apostles proclaimed was a new human world, a new social and political reality. In other words, a salvation. God has established the eschatological order of human life in the midst of history, not perfectly but truly. The Church anticipates the form of the human race as it will be when it comes to maturity. Conversion thus means turning from one way of life, one culture, to another and our 'resocialisation' into an alternative paideia. 
In the NT, we don't find a two story house. 1st story: private faith. 2nd story: public implications. The gospel is the announcement of the Father's formation, through His Son and the Spirit, of a new city - the City of God. 

(Against Christianity p13-16)