Piper, a Calvinist, discusses God’s two wills in his review of God’s Strategy in Human History:
D. F&M cite many texts in which “not all men do God’s will” (31.4). They conclude from these verses (e.g. Luke 7:30; Matthew 23:37; 12:50; 7:21; John 7:17; 1 John 2:17; 1 Thessalonians 4:3, 5:17-19; Acts 7:51) that a man can thwart the will of God for him. If Jesus says that only those who do the will of his Father in heaven will enter into the Kingdom then there are many who do not do the will of God. F&M conclude: “Nothing in Scripture suggests that there is some kind of will or plan of God which is inviolable” (32.3, see “E” below for Scriptures which do indeed suggest this!). They reject any attempt to distinguish between two ways that the will or counsel of God is conceived (32.33). But in doing this they reject a theological construction which in my opinion handles the data of Scripture more coherently than the theological construction of free will and the thwartable God.
A careful reflection upon the Scriptures compels us to distinguish between different senses in which the will of God is spoken of. Calvin uses the terms “signified will” and “effectual will” (32). Jonathan Edwards refers to God’s “secret will” and his “revealed will” or, which is perhaps most apt, God’s “will of decree” and his “will of command.” The stumbling block for the Arminians has always been that Calvinists assert that God can command one thing and decree that another thing come to pass; he can say that one thing is his will and yet foreordain a contrary thing. But is this not in fact so?
Let’s take the example of Pharaoh’s hardening of heart. It is irrelevant for the present point whether F&M are right to translate “harden” as “strengthen.” What is important is simply this: to F&M after the fifth plague God gave Pharaoh “supernatural strength to continue with his evil path of rebellion” (73.9). In other words, it was God’s will that for five more plagues Pharaoh not let the people of Israel go. Nevertheless even after God had willed not to let Israel go for five more plagues, “The Lord said to Moses ‘Go to Pharaoh and say to him, “Thus says the Lord, Let my people go!””‘ (Exodus 8:1). Here is a clear example of where God’s “will of decree” and “will of command” have to be distinguished.