The difference between the Reformed and the Arminians lies
not in whether there are two wills in God, but in what they say this
higher commitment is. What does God will more than saving all?
The answer the Arminians give is that human self-determination and the possible resulting love relationship with God are more valuable than saving all people by sovereign, efficacious grace. The answer the Reformed give is that the greater value is the manifestationof the full range of God’s glory in wrath and mercy (Rom. 9:22–23) and the humbling of man so that he enjoys giving all credit to God for his salvation (1 Cor. 1:29).
John Piper
From the book “Does God Desire All to Be Saved?”