This is Jonathon Edwards Jr, the son of the revivalist Jonathon Edwards Sr, on why the atonement of Christ was necessary in order for the forgiveness of sins.
This is such a brilliant answer from the governmental atonement camp against the heresy of Socinianism.
The Socinians said that if sin is merely a matter of personal offense to God, just like any other person God can freely pardon it without any need for an atoning sacrifice.
Moral Government refutes this by showing that law and penalty is governmental with governmental purposes and if our penalty is going to be remitted in the pardon of sin, an atonement must substitute our penalty and fulfill its governmental purposes.
The atonement is a justification for the mercy of God, so that forgiveness does not conflict with public justice (Rom. 3:24-26).
An atonement is necessary for the same reason punishment would have been necessary, since atonement is a substitute for punishment.
This shows the genius of God and why “without shedding of blood is no remission” (Heb. 9:22).
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This is why it is important to ask, “Why does God punish sin?” Is it to gratify His personal feelings of wrath and anger? No, but to maintain the honor and authority of His law for the good of His universe. Punishment is a public example to deter others. The atonement, as a substitute for punishment, accomplishes the same thing.