I re-post here my comments on the next question of the WSC, which I wrote up two years ago:
Q7. What are God’s decrees?
A. The decrees of God are His eternal plan, based on the purpose of His will, by which, for His own glory, He has foreordained everything that happens.
Let me here promote, as I should have done more forcefully and consistently before, the use and advantage of Training Hearts, Teaching Minds as a family worship resource. If you yourself are uncomfortable about how to unpack theological topics like election, predestination, and reprobation — or if you just don’t know how to explain them to your four-year-old — THTM can be an invaluable guide.
What THTM does, and what I would do, is rely on earlier truths established by the former catechism questions, and show how this truth is a logical extension of them. God is infinitely just, wise, powerful, holy, and true, and He has been so and will be so, unchanging, for all eternity. He is the one — and only one — delike this, the only one worthy of all glory. Indeed, our purpose is to glorify Him, but we fail in that purpose. What is to be done?
God has already done it. He has had a plan in place before creation, before time. He not only knew, omnisciently, all that will happen, but everything happened as He planned it ahead of time (foreordained). His very triune personhood reflects this eternal intentionality. And His plan is so awesome, so wonderful, it is the ultimate expression of who He is, His glory, and it brings us back into our purpose, to glorify and enjoy Him.