The Folly of Legalism

How could the Galatians be so stupid that they would exchange the utter sufficiency of God's grace for a salvation based on observing the Jewish law? It must be that they are under some kind of spell that they could forget the cross and all it had meant to them when they first came to faith. How could they imagine they could make an improvement on what Christ accomplished in His death in making atonement for the sins of the world? The way the Spirit was poured on them was positive proof that it was all of grace and not by law observance.
Church history, and often our own experience of growing up with a deficient gospel, show us how easily we are hood-winked into relying again on human effort instead of continuing in the Spirit - forgetting that it is not on the basis of works that we are declared righteous but on the basis of faith. How can we, in even the smallest way, suggest that something we can do can stand alongside God's unparalleled action of grace that we see so clearly in the cross? Ultimately, it is seeing Christ bearing the curse of the law's judgement so that we Gentiles might receive all of what God promised to Abraham by faith which shows us the utter futility of trying to receive God's promised blessing any other way.