Penal substitution takes a lot of flack these days. Many of the objections that come up against PSA have focused on this theories assumptions about what justice is. However, many of these objections are based upon what we tend to think justice is. But as Donald Macleod has said,
It would be certainly perilous to judge the cross by the wisdome of a prevailing culture. From the standpoint of divine revelation the logic must go in the exact opposite direction, allowing the cross to be itself the judge of the culture. This is what Luther meant when he declared, cruz probat omnia (the cross is the test of everything)…
Some object that PSA portrays God as bound to some abstract notion of justice. As if he were ruled by some universal law of justice…
But this gets God and justice all mixed up. God’s righteousness, his justice is not external to who he is. It is not something that exists outside of God. Righteousness is what God is. To say that God acts justly or that God requires penal subsitution (or satsifaction) is to say that God is simply acting out his nature. God acts justly, not because he is required to, God acts justly simply because God just is just….
Some object that PSA operates outside of a biblical understanding of justice. The classical idea of justice is that people get what they deserve – reward if they are good, punishment if they are bad. Biblical justice is about protection, salvation, and solidarity – its about God’s covenental commitment to his people’s well-being.
Again this is simply wrong. This objection is grounded in a modern aversion to justice as retribution (justice certainly is much bigger in scope than mere retribution, but retribution can certainly be a part of what justice is). This objection also splits God’s covenental commitment into two categories that are non-existent in scripture. God’s covenental commitment to his people is not only about God overseeing the well-being of his people its also about his own righteousness. These two things cannot be separated. Because of God’s righteousness God is justified in punishing when the covenant with him is broken. There is no split between God’s righteousness and his covenant.
Now Penal Substitution has been objected for various reasons, justice only being one of them. As we can see, these two simple objections miss the mark when it comes to atonement and justice.