Adoption and penal substitution

Here's a neglected argument for penal substitution. The NT says Christians are heirs. And inheritance has a vicarious dimension. An heir is the beneficiary of someone else's action. An heir needn't do anything to be the beneficiary. He can simply be an heir in virtue of his relation to someone else who did something. An heir typically has an ascribed status rather than an achieved status. A status conferred on him in relation to someone else.

According to the NT, Christians are heirs in virtue of their union with Jesus. And by reason of that relation, they are heirs of salvation rather than damnation. They escape eschatological judgment they are God's adopted sons, and they enjoy that status in virtue of what God's ontological Son did on their behalf. So that has a penal dimension as well as a vicarious dimension.