I notice that C Everett Koop died a week ago yesterday. The Times has an obituary today. You can freely access this Washington Post obituary here. I was aware of him because of the pro-life films he did with Francis Schaeffer. He was a longstanding member of Tenth Presbyterian and came to prominence as President Reagan's Surgeon General.
Bonhoeffer uses a similar phrase 'worldly Christianity'. It's J Gresham Machen that I want to line up most closely with. See his Christianity and culture here. Having done commentaries on Proverbs (Heavenly Wisdom) and Song of Songs (Heavenly Love), a matching title for Ecclesiastes would be Heavenly Worldliness. For my stance on worldliness, see 3 posts here.