The Atonement: Penal-Substitution

THEOLOGIAN: Anselm (c. 1033 - 1109) Archbishop, Saint, and Theologian.
WORK ON SUBJECT: Cur Deus Homo [1]
ANGLE: Juridical
THEME: Godward (understands the work of Christ as primarily addressing a necessary demand of God [2])
IN HIS OWN WORDS:

"It may, indeed be said, that the Father commanded him to die, when he enjoined that upon him on account of which he met death. It was in this sense, then, that "as the Father gave him the commandment, so he did, and the cup which He gave to him, he drank; and he was made obedient to the Father, even unto death;" and thus "he learned obedience from the things which he suffered," that is, how far obedience should be maintained." [3]

Basically...

The basic premise of this theory is expressed quite often in certain circles when discussing how Jesus died in our place. As the name of the theory suggests, Jesus died on the cross as man's substitute. Often, John 3:16 is quote in this way:

For this is how God loved the world: He gave his one and only Son, so that everyone who believes in him will not perish but have eternal life. —John 3:16, NLT

A lot of times it is explained as a simple switch, but that's not all that is at play here. In fact, the parts that involve mankind are actually quite small. This theory has everything to do with God's Holiness and Wrath. Hence, why it has been said that the theme of this view is Godward.

God, as a holy and just judge of this world, must condemn sin when he sees it—and he sees it covering his creation. God's wrath is kindled against Man. It says so in the Bible:

For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men who suppress the truth in unrighteousness. —Romans 1:18, NASB

According to the natural course of justice, God must pour out the full measure of his wrath on human beings for their rebellion. But there is another way. The substitutionary sacrifice of Jesus Christ, best explained (again) in Romans:

being justified as a gift by His grace through the redemption which is in Christ Jesus; whom God displayed publicly as a propitiation in His blood through faith. This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed; for the demonstration, I say, of His righteousness at the present time, so that He would be just and the justifier of the one who has faith in Jesus. —Romans 3:24-26, NASB

This brings us to another important word for this theory: Justification. The end-goal of this theory (from man's perspective) is to get us to the point where we can stand justified before God. To be justified is a legal term that declares the man/woman righteous by imputation. God looks at us, we point to Jesus, and God says, "OK, He's righteous so I'm satisfied." The end-goal of this theory then (from God's perspective) is to have his wrath (and love) satisfied.

Or consider this outline from Saint Anselm:

(1) The essence of sin is humanity's failure to render to God what is rightfully due him; sin dishonors God.
(2) It is humanity's responsibility to restore to God what they have robbed him of, as well as to make reparation above and beyond for injuring and offending him. God's honor inherently demands such restoration and reparation.
(3) Humanity can never restore such a debt. Even if humans did their best and did not sin further, they would only be rendering what God is already due; the necessary reparation above and beyond would always be left undone. Beyond this, humanity lives in a state of bondage to the devil.
(4) God is left with two basic options: punish humanity as they deserve, or accept satisfaction made on their behalf.
(5) But now the predicament: satisfaction can only be made by a human since it is humanity that owes God the debt, yet no mere human has the resources to make satisfaction for the race.
(6) The sole solution is to be found in the mystery of Jesus Christ, the God-man. As God, he has the ability to make satisfaction; as man, his satisfaction can be made on behalf of humanity. [2]

* It should be clarified at this point that while Anselm certainly laid the groundwork for the many subsequent objective theories of The Atonement, it did not develop into properly understood Penal-Substitution until John Calvin and the Reformers. Yet, they can be looked at as developers of a theory more than innovators of one.

Precedent

Related to the comment about love, the tension between God's wrath and God's love is ever-present in scripture. In the OT, God is constantly vacillating between burning anger and burning desire for his people. He gets angry but preserves a remnant. Even before he establishes Israel, God floods the earth but saves Noah. When these two elements are viewed in tandem, God places himself in an apparent bind. He cannot uphold one without violating the other. But he cleverly finds a way to uphold both by the perfect sacrifice of his son.

Problems

Proponents of this theory may have a tendency to emphasize the wrath of God at the expense of his love. A punishment must be made, God must be satisfied. Some very important attributes of God must then be minimized in order to amplify this part of the truth.

The idea of justification and imputed righteousness leaves this theory open to the charge of neglecting the sanctification of the believer. It leaves the Christian justified, but not intrinsically righteous. In that sense, it's only a covering or deflection and not a removal of sin. Thus, the fragmentation of salvation into justification then sanctification becomes a major new contribution made by this theory.

Conclusion

This theory is very personal. Jesus becomes the substitute for me so I can read my name into John 3:16. A lot of the ideas in the Penal-Substitution Theory of Atonement certainly lends itself to the individualism we see in current Christendom and leads to even more theological innovation when taken as the sole basis of Atonement Theology. A lot is happening when man's sinful state is atoned for, especially from God's perspective.

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References: 

1. "Anselm (c. 1033 - 1109)." In Who's Who in Christianity, Routledge, by Lavinia Cohn-Sherbok. 2nd ed. Routledge, 2001.
2. Eddy, P R., and J Beilby. "Atonement." In Global Dictionary of Theology, edited by William A. Dyrness, and Veli-Matti Kärkkäinen. InterVarsity Press, 2008.
3. Anselm. "Cur Deus Homo?" https://www.ewtn.com/library/CHRIST/CURDEUS.HTM