If forgiveness is cheap, then peace is not possible because we can simply perpetuate our offenses and oppression of others in the hope or anticipation that by asking for forgiveness we will receive it. An intellectual assent to that idea is held to be of itself sufficient to secure remission of sin. The Church which holds the correct doctrine of grace has, it is supposed, ipso facto a part in that grace. Cheap grace therefore amounts to a denial of the living Word of God, in fact, a denial of the Incarnation of the Word of God. Cheap grace means the justification of sin without the justification of the sinner.
Grace alone does everything, they say, and so everything can remain as it was before.
All for sin could not atone. Well, then, let the Christian lie like the rest of the world, let him model himself on the world's standards in every sphere of life, and not presumptuously aspire to live a different life under grace from his old life under sin. That was the heresy of the enthusiasts, the Anabaptists and their kind. Let the Christian beware of rebelling against the free and boundless grace of God and desecrating it. That is what we mean by cheap grace, the grace which amounts to the justification of sin without the justification of the repentant sinner who departs from sin and from whom sin departs.