I thought we'd finish the series with some hats. People don't wear hats as much these days as they once did. When I look at the two hats above I immediately think Bampie, Grandad. My Grandad Brady was 6" 4' an inspector in a steelworks and wore the trilby, my Bampie Thomas a council workman was 5" 1' and wore the flat cap.
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.