I'm in W H Smith, waiting in the queue to pay for my paper. The man in front of me says "two boxes of unbelief, please". I think to myself "it's come to this. You can even buy unbelief over the counter". Then I thought "I've probably misheard him". I had. He wanted cigarettes.
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.