This essay attempts to explain the belief that the death of Christ on the cross had the character of penal substitution, and that it was by virtue of this fact that it brought salvation to mankind. First, the author clears up some questions of method. He then continues to explore what it means to call Christ's death substitutionary. In the third place, he considers what further meaning is added when Christ's substitutionary suffering is called penal. In the last instance, Packer notes that the analysis he offers is exegetically well-founded.