As a footnote to last week's post, let me add something here: to say that God is continuously sustaining all the elements of the universe is not to say He controls every human act.
To sustain and to control are two different things. If I punch you in the nose, I trust you won't think God made me do it. While He will sustain my fist if I choose to connect it with your face, don't assume He is causing me to swing, or that this particular act was planned by Him from the foundation of the world. God gives His image-bearers, as Thomas Aquinas put it, "the dignity of causality."
While God is in a position of absolute control (that is to say, if He wanted to, God could turn my arm into Jello before impact, or send an angel to divert my aim), He does not control every act of humanity absolutely. I know I'm wading into controversial waters here, but the idea that everything that happens is "the will of God" is fatalism.
Back to the "sacred-secular split."
The second big help I've found in shedding the "sacred-secular distinction," is the acceptance of God's universal ownership. That is, the earth and everything in it belongs to Him. Not just the mountains, the rivers and the apple trees, but the ring on my finger, the shirt on my back, and the roof over my head. All the oil in every reserve, all the gold in Fort Knox, and whatever you may have in your checking account is His, along with all the cars on the freeway, the jets in the sky, and every person who drives or flys them.
"The earth is the Lord's, and all it contains, the world and those who dwell therein." [Psalm 24:1] This is God's world! Furthermore, He gives every human breath (Job 12:10), and "in Him we live and move and have our being (Acts 17:24-28)."
So where exactly is the secular world?
Yet, as a student at the University of Washington, I attended a "secular school," didn't I? When I worked during the summers unloading box cars on the Seattle waterfront, I had a "secular job," didn't I?
Well...no. I'll explain why next week.