The early theories that we have considered (Ransom or Classic and Satisfaction) have similarities with the Penal Substitution Theory. In all of them, Jesus becomes a kind of victim, offered up on behalf of all humanity through his death, in execution fashion, on a cross. This is required, many have said, as a way for God to take sin seriously and have God's own sense of honor and justice restored. It all boils down to the idea that God will only be happy through a slaughter-type arrangement of God's Son. There is no way to dress up these theories and make them palatable. To view the cross in this way brings God off as an ogre.
But in the Penal Substitution approach, the death of Jesus is not so much a sacrifice as a payment to God for the debt owed by humanity because of sin. A price HAS to be paid for wrong-doing. We have sung in worship "Jesus paid it all." (Beautiful melody with questionable theology). This would be what God required and Jesus was willing.
This theory came into being with full force during the Reformation under the tutelage of John Calvin. Calvin would write in his major work, "No-it was expedient at the same time for him to undergo the severity of God's vengeance, to appease his wrath and satisfy his just judgment. For this reason, he must also grapple hand to hand with the armies of hell and the dread of everlasting death...He suffered the death that God in his wrath had inflicted upon the wicked!...'My God, my God, why hast though forsaken me?'" (Institutes II, 16,10f)
I remember hearing this illustrated in a legal way. Humanity stands in the courtroom before a Just and Holy God. All are pronounced guilty. They deserve to pay the ultimate price of death and eternal punishment. But then a strange thing happens. The Judge (In the person of Jesus) steps out from behind the bench and says, "I will suffer all this for you." Jesus becomes our substitute and pays the price for our sin.
A couple of things to note: First, there is that sticky, tricky issue of the Judge being God, but really being Jesus. If God did all this, did that mean that God was dead for three days as was Jesus. Imagine, a world without God for 72 hours.
We can't have it both ways. Either Jesus is God and therefore an absent God for a stretch or Jesus is separate from God.
Secondly, based on what else we have understood as a truth streaming its way through our history, why could not this God/Judge of UNCONDITIONAL LOVE say, "I love you too much to let you go. All is forgiven. Let's go home together?"