Brain of Britain is on Radio 4 at present, on Mondays at 1.30 pm. They always have a bit where a listener puts two questions to the contestants who work together to try and answer him. A little while ago I sent off two questions and I now hear that they are to be tackled on Monday January 24. Do listen if you can. It's repeated late Saturday night and will be on iplayer for a while. I notice that there's a Bruce Ware lecture at LTS that I hope to hear when the programme is first broadcast (on providence!!) so I have a dilemma. I would expect them to work out the answer to both questions but we'll see. May be I'll get a book token.
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.