In the twentieth century the Reformed tradition was developed in several ways including additional confessions (Barmen, the Belhar Confession, the 1967 Confession of the PC(USA), and so on). It was also significantly augmented by the work of important thinkers like Karl Barth, T. F. Torrance, Jürgen Moltmann, Emil Brunner, Kathryn Tanner, and so on.

Now, don't get me wrong: I'm not rubbishing penal substitution. But there are other options that have been advocated by Reformed thinkers of the past.

One of the things we in the Reformed tradition are very good at is writing doctrinal theology!

Jonathan Edwards developed a Calvinistic strand of the doctrine.

[ Jonathan] Edwards is one of my heroes. I've learned much from him over the years.

In the chapter on the nature of the atonement [in the book saving Calvinism] I argue that it is a mistake to think that penal substitution is the only option on the doctrine of atonement.

No confession is inerrant; Reformed Christians are supposed to be those who seek to be constantly reformed according to the Word of God - and that includes our confessions as well.