What’s the Purpose of the Law if we can’t actually keep it? On Missional Ethics and Deuteronomy

I am reading a book on mission ethics in the Bible. It strikes me that there is actually a very clear and strong logic for mission ethics in Deuteronomy. Here’s the bottom line:

1. We can’t save ourselves.
2. God saves us.
3. God wants us to observe the Law given by Him.
4. The Law doesn’t/can’t save us.
5. The Law is for us to live a new and good life, which is defined as a life relying on God (hence we need to remember God, and live according to His commandments).
6. Our new life witnesses to God’s power to save and transform.
7. The way we live the new life (ethics) demonstrate God and God’s realm.
8. Since we testify for God, our new life is missional.

All of the above can be easily derived from Deuteronomy. For those who are familiar with the book, you can even see the relevant chapters and contents as you browse through the list.

And there will be the question of “violence” in the mix of this. That will be for another post.

Of course the New Testament gives us more clue on how all these work out in the grand narrative of God’s salvation plan, but how often do you notice logic of mission ethics in Deuteronomy?