I would say that the most foundational error in the book is his rejection of the “dual aspects of the covenant” (55-56), a matter which I consider essential to good Reformed theology and well balanced Calvinism. Reformed theology at its best accepts all that Scripture teaches about both divine sovereignty and human responsibility, even though tying this all together in a neat logical system transcends human rational ability. From the perspective of divine sovereignty, the covenant of grace is God’s unconditional plan to accomplish salvation for the elect through the finished work of Christ and to apply that salvation to the elect through the efficacious work of the Spirit. From the perspective of human responsibility, the covenant of grace is a historical administration which involves means and obligations and which not only decisively impacts the lives of the elect but also affects in varying degrees the lives of many non-elect.
These dual aspects also apply to the church. The church in its invisible aspect is the church from the perspective of God’s secret decretive will, the church as only God can see it. The church in its visible aspect is the church from the perspective of its human administration as regulated by the principles of God’s revealed preceptive will.
—Grover Gunn, “A Review: The Baptized Body” (HT: Aquila Report)