We had lunch together yesterday as we do from time to time. Always a good time, although numbers were down rather on this occasion. Some were unwell and one or two were away and although the were some visitors not all stayed. In the morning I preached chiefly on church disciplines from 1 Corinthians 5 and then in the evening some 16 were present to hear the last of the series on Numbers 36, considering our heritage in Christ. One unusual thing was four little girls in the Sunday School. I can't remember when we had so many girls around.
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.