from Michael Bird:
The cross is penal, don't believe me, consider this: "For what the law was powerless to do because it was weakened by the flesh, God did by sending his own Son in the likeness of sinful flesh to be a sin offering. And so he condemned sin in the flesh, in order that the righteous requirement of the law might be fully met in us, who do not live according to the flesh but according to the Spirit" (Rom 8:3-4 NIV).
The cross is substitutionary, don't believe me: read this: "'He himself bore our sins' in his body on the cross, so that we might die to sins and live for righteousness; 'by his wounds you have been healed.'" (1 Pet 2:24 NIV).
Look, I know that penal substitution can be presented woefully and inadequately, whereby God gets revenge on Jesus for your sins, so you better buy some fire insurance, otherwise you will roast forever in the deity's dumpster of destruction. I would even be prepared to say that penal substitionary is not the primary descriptor for the atonement, it is at best a major part of the mosaic that is the atonement.... However, there is no possible way I can stupefy my mind to deny what these few texts are saying. Now, if you want to say, well, the NT authors are just wrong, and I think Peter Abelard, Hastings Rashdall, and Tony Jones know better, then fine, go for it. But don't draw a circle on the board and tell me to call it a square!
The entire post is here.