I found Christopher Green’s comparison between the views of the two theological giants that were Francis Turretin and Karl Barth regarding God’s sovereignty vis-à-vis evil very illuminating, so I thought I would share it. Green writes:
In the traditional teaching, the orthodox make a hamartiological distinction in order to accommodate the providentia circa malum [providence in relation to evil], between an “order of being” and an “order of morals.” The order of being is the proper object of the voluntas beneplaciti [God’s decretive will] in the providential disposing of all created things. That is, as God orders all events according to his will, these events are arranged to align with his will according to their being. Since opposition against God’s will is impossible, he reveals the sin which opposes him through a different will, that is the voluntas signi [God’s prescriptive will]. It is in this domain that the will of God may be resisted. Sin may take place, then, in the context of an order of morals, and the creature’s being may still be secure beneath God’s sovereignty. The ethical domain must be kept separate for the orthodox, as God providentially allows the creature to choose sin but does not condone it in the sense of his actio. With another reversal, Barth asserts that the creature’s acknowledgment that all of creation is one order is a matter of thankful obedience to Christ.
Francis Turretin, as an example of an orthodox thinker, finds that the order of morals is the arena where God reveals his opposition against sin. Turretin states: “In every moral action we must necessarily distinguish the substance of the act in the genus of being from the goodness and wickedness of the same in the genus of morals.” It is on the basis of this distinction that God can be said to change his mind in the biblical narratives, as the voluntas signi does not univocally echo the will of God ad intra. Turretin continues:
Thus the volition of stealing reduplicatively and circumstantiated here and now, is indeed essentially evil with regard to another’s property; but the volition, to which that circumstance happens by which it is a volition to steal, is not essentially evil in like manner […] God was unwilling that the brethren of Joseph should sell him and that the Jews should crucify Christ, since they were most heinous crimes against the law. Yet he is said to have willed, yea, even to have done these things. (Gen. 45:7; Acts 4:28) [Institutes of Elenctic Theology, vol. 1, p.510-511]
Importantly, this position leads Turretin to make statements similar to those belonging to Barth during the Göttingen period. In some sense, God must be said to be the “cause” of sin. In this manner, Turretin’s explication of the providentia circa malum describes the situation that originally causes Barth to suspect a difficulty with the orthodox position with respect to divine holiness. When this same strain begins to show in Turretin’s writing, he reiterates the distinction between an order of being and of morals. Turretin states:
God is the cause of the human will; therefore he is the cause of sin—for when the created will sins, it turns aside and fails from the order of the first cause. And God who is the cause of the will per se, cannot be called the cause of the evil action, which is from the will not simply in the genus of being (as it is from God), but from the will failing as to the law in the genus of morals. [Institutes of Elenctic Theology, vol. 1, p.525]
Barth’s repudiation of the orthodox position on the will of God has implications for all of creaturely life, life that undergoes both moral and immoral action. Consistent with Barth’s position on the voluntas beneplaciti and signi, he invests both the being of the creature and her ethical life in her response to the self-revelation of God in Jesus Christ. Since the dual-order structure in the life of God has been merged in Christ, the very essence of the creature must also be said to be equivalent with his own act of praise: “Gratitude is to be understood not only as a quality and an activity but as the very being and essence of this creature.” Barth’s position comes full circle in this way: praise is the realization of God’s will not only for the creature’s moral life, but for his physical being as well. Sin can never be a power in the hands of the creature, enabling it to establish a secondary order outside the sovereign Creator’s will: “Thus we must not focus our attention on the sinner, as though by his sin he had founded a new order of things which had an independent meaning.” Rather, “by doing this and this alone does he distinguish himself as being from non-being […] ‘To be or not to be? that is the question’ and it is decided by the way in which we answer the question: To give thanks or not to give thanks?”
I wish to make no other comment on this than to simply reiterate the final question posed by Barth via Green: which of these ways of conceiving God’s relationship to the ever-present problem of evil provide us with this greatest grounds for living life doxologically, in praise and gratitude for all of the ways and works of God?
I leave it to you to ponder this question.
 Green, C.C., 2011. Doxological Theology: Karl Barth on Divine Providence, Evil, and the Angels J. Webster, I. A. McFarland, & I. Davidson, eds., London; New York: T&T Clark. pp.33-35.