Kevin De Young has a piece over at TGC on Is John Piper Really Reformed?
I think De Young’s argument is basically correct and he gives helpful nuance to the diversity of Calvinistic and Reformed churches in North America
But there are two issues here:
First, the definition of “Reformed” is slippery. For some it basically means “Not Catholic.” For others it means Calvin and only Calvin. Then again, some see being Reformed as tied to covenant theology. For others it means holding to one of the Reformed confessions (Belgic, Westminster, Augsburg, 39 Articles, etc.). Though I had an interesting chat with my colleague Rhys Bezzant the other day who suggested that the essence of Reformed thought is seeing one continuous plan to salvation across the testaments.