Bear with each other and forgive whatever grievances you may have against one another. Forgive as the Lord forgave you.
(Colossians 3:13)

In the book of Colossians, Paul instructs the believers that they should "forgive" each other "as the Lord" has forgiven them. This is a high calling–forgive even as God has forgiven! However, the immediate question comes to mind: what does it mean to forgive "even as" God has forgiven?
Penal substitutionary atonement (PSA) theory holds that all sin creates a "penalty" which must be "paid" in order for the sin to be forgiven. As all of humanity has sinned, PSA theory asserts that all owe a "penalty" for said sin, a penalty which must be paid if forgiveness is to be actualized. But to whom must the penalty be "paid?" Surely it is not Satan, for it is inconsistent to say that forgiveness of sins is secured upon paying off the devil. Therefore, the only one to whom the payment can be due is God.

So then, PSA theory holds that humanity owes a "penalty" for its sin to God. As the penalty requires satisfaction, only payment of the penalty will secure forgiveness. Moreover, PSA theory asserts that God will not remit the penalty of sin, but rather requires satisfaction of the penalty (as God is not bound by any contingency and is entirely free in all of the decisions that God makes, it must be asserted that God can remit the penalty, but will not–therefore, the refusal to forgive [remit the penalty] is based on God's free choice, not any necessity).

So if God will not remit the penalty of sin, how is forgiveness to occur? PSA theory insists that Christ, in his death upon the cross, has somehow "paid" the penalty that all of humanity owes to God for sin.
On the surface, this theory appears to be quite reasonable, especially given the fact that it coincides nicely with a modern, Western conception of "justice." The appeal of this theory can be especially seen in the fact that for most Western Protestant denominations, PSA theory is the Atonement theory.
However, if one peers a bit closer into what is actually occuring within PSA theory, horrfic theological consequences become readily apparent.

1. PSA theory creates a disunion in the divine will: Christ, in the cross, reveals a will to forgive humanity. However, God, apart from the cross, has no such will. In fact, God's will is precisely set to not forgive sin, as God could but will not remit the penalty. Therefore, Christ, in the cross, is shown to do that which the Godhead, apart from the cross, is not willing to do.

2. If Christ remits the penalty, his sacrifice blackmails God and compels the forgiveness of sin: As shown, God, apart from the cross, does not desire to forgive humanity's sin. However, Christ, in the cross, secures the satisfaction of sin by paying the universal penalty of sin. Therefore, by virtue of Christ's sacrifice (which is naturally opposed to the will of God), Christ literally compels the forgiveness of sins from God. This is necessary, for God, apart from the cross, is unwilling to forgive sins. Therefore, forgiveness of sins in response to Christ's rebellion against the divine will on the cross is not based upon a free choice (for God could forgive sins without condition, but will not), but rather upon certain conditions being fulfilled which actually violate the nature will of God concerning human sin. In this way, Christ, in his death, literally blackmails God, for God is no longer free to forgive or withhold forgiveness; rather, God must now forgive sins because Christ has fulfilled a set of conditions which forcefully compel action from God.

So let's take these two (and there are many more that could be noted) consequences of PSA theory and apply them to the command to "forgive" as God has forgiven. If PSA theory is the correct paradigm for understanding and disseminating forgiveness to others "as" we have been forgiven, a couple of disturbing necessarily surface.

1. Our forgiveness of sins must be based upon the other person "satisfying" the penalty of their sin against us: As we have been forgiven by God based upon the satisfaction of a penalty, so our forgiveness of others must be conditioned by this criterion as well. Therefore, if the one seeking forgiveness does not "pay" the penalty for the sin to a satisfactory extent, it would be quite improper to grant them forgiveness as this is not the way in which PSA theory supposes humanity to have been forgiven by God.

2. Our forgiveness of sins must be "automatic" if the conditions of forgiveness are met: As God is compelled to forgive us because Christ has fulfilled the conditions for our forgiveness, so too must our forgiveness of sin flow from necessity.

In my estimation, PSA theory fails significantly in providing a helpful foil for understanding the relationship between God's example of forgiveness and the command to forgive "as God has forgiven." Within this paradigm, there is no room for freedom or for love; rather, forgiveness is based upon and mediated by certain conditions and prerequisites being fulfilled. I personally believe that this is an entirely un-biblical picture of God's forgiveness which has been manifestly revealed in the complete and utter self-giving love of Christ. I think of Christ looking down upon his murderers in love: in this moment, there is no conderation of "conditions," no evaluation of whether or not these individuals have met the necessary prerequisites to be forgiven. Rather, Christ abandons any pretentions of what is "owed" to him and freely and completely extends forgiveness, and the invitation to reconciliation. This should be the lens through which we seek to understand and, more importantly, practice forgiveness. Using a paradigm such as PSA theory does not provide a robust conception of forgiveness, and greatly restricts the freedom and love which ought to be extended, even as it has been extended to us. In this way, the cross must become a picture not of the "conditions" which have been met to secure forgiveness, but rather the awesome and penetrating display of the true nature of forgiveness–a absolute self-giving love that, even in death and rejection, seeks reconciliation and restoration of relationship.