The Incompatibility of Works and Faith

Paul has argued that the experience of the Spirit should have been enough to clue for the Galatians to know that they belong to the people of God. Why, then, is he so against the idea that some want more assurance? What if circumcision helps the weak in faith; what is so wrong with that? It this practice not a helpful way to encourage them in the faith, to keep them assured of their inheritance from Abraham? Paul has argued positively, that the Spirit is assurance enough. He will know begin to argue negatively that any mixture of works stands against faith. Works and faith are incompatible.