You are right in saying that Catherine Marshall's views are a bit 'off'. That seems to have really sped up after the death of her husband. When I said above that Marshall's sermons were different, they are. They are not theological treatises. As such, it is not possible to put together a systematic theology by them. I am not a Peter Marshall expert, but in the sermons that I have read and heard he holds a very high view of God's holiness, stresses the fallen nature of man, and the necessity of redemption by grace alone.