I'm listening to Desert Island Discs on Radio 4 at the moment (the repeat) and Kirsty Young is talking to the animator Oliver Postgate (Bagpuss, Noggin the nog, clangers). His seventh choice, just played, is the beautiful Introspection 2 by Thijs Van Leer. I've never heard a Van Leer track on the radio before. About time. Let's hear more. See here.
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.