I was reading the other day about Julian the Apostate, Roman Emperor 361 to 363. He was called the Apostate because he attempted to take the Roman empire back from Constantinian Christianity to paganism. His reign was cut short by his death during the Battle of Ctesiphon in Persia in June of 363. I had heard that rumour, probably started by Christians, that he died with the words "You have won, Galilaean" on his lips. More interesting I think is the fact that he died (from a spear wound) because he had not worn any armour, either through confidence of a victory or through haste or forgetfulness. That's an illustration I'll be using.
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.