It is interesting that Lutheran dogmaticians use different categories for classifying the attributes of God than do the reformed. The reformed typically discuss the communicable and incommunicable attributes of God. Pieper however classifies them as positive and negative attributes. Those attributes which are positive things which we have in part such as love, holiness, justice etc. Negative attributes are those attributes of God which are known negatively, or as opposed to our own attributes. These would include omnipresence, omniscience, etc. Pieper is correct in saying that how one classifies these attributes is not particularly important. Theologians are free to use different categories to discuss biblical truths.
Pieper then discusses the doctrine of creation. He opposes the doctrine of Augustine and other fathers who claim that the six days are a mere literary device to describe God's creation. He argues that those Christians who subscribe to evolutionary theories are putting the truths of science over God's word. Here is where I think Pieper goes too far. Science can find legitimate truths. When science finds something which disagrees with scripture, either the result of science is wrong, or one's interpretation of scripture is wrong. Pieper does not seem to be able to admit that perhaps his interpretation of scripture is wrong. He goes so far as to argue for geocentrism in a footnote. (pg. 473) I do not buy into evolutionary theory, however, I do not have a problem seeing the days as a literary device. The problem is never with scripture but with our interpretation of it. We must admit our interpretation as fallible.
Pieper's section on divine providence admits that God's providence extends over all things that happen. He deals with the problem of God's sovereignty over sin in a particularly good way. He states that God is sovereign over man's sinful actions so far as they are actions, but not so far as they are sin. This protects God from causing sin, but preserves his sovereignty. Pieper at this point leaves it to mystery.