I do not remember the first time I heard someone say that Western society represents a post-Christian culture. If he was correct, then the West represents a tragedy. In Hebrews 6:6, the inspired writer ominously warns first-century Christians against falling away from the faith, and does so based on the tragic condition of one who is lost:
For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, and have tasted the good word of God, and the powers of the world to come, if they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
Do not be bothered by the word “impossible” in this verse. The language actually means that it is impossible for someone to be renewed while crucifying the Son of God. ((See Wayne Jackson, “Are Apostates from the Faith beyond Repentance,” https://www.christiancourier.com/articles/682-are-apostates-from-the-faith-beyond-repentance (n.d.).)) That is, while a person has a rebellious attitude toward God, he cannot be saved.
Still, anyone who repents can be saved (Acts 2:38, 17:30). An implication of Hebrews 6:6 is that an entire culture of people who have experienced Christianity, and then passed on to a spiritual occupation they think better, is a disaster. C.S. Lewis speculates that the only solution for such a culture is to pass away and leave a new generation which has not yet “tasted the good word of God”:
When grave persons express their fear that England is relapsing in Paganism, I am tempted to reply, ‘Would that she were.’ For I do not think it at all likely that we shall ever see Parlaiment opened by the slaughtering of a garlanded white bull in the House of Lords or Cabinet Ministers leaving sandwiches in Hyde Park as an offering for the Dryads. If such a state of affairs came about, then the Christian apologist would have something to work on. For a Pagan … is essentially the pre-Christian, or sub-Christian religious man. The post-Christian man of our day differs from Him as much as a divorcée differs from a virgin. ((“Is Theism Important?,” God in the Dock, ed. Walter Hooper (Grand Rapids: Eerdmans, 1970), 172.))
Is Western society really a post-Christian culture? This is a complicated question. On the one-hand, many people seem to think it is so. ((E.g., Howard Kains, “The Christian Vestiges of Post-Christianity,” Crisis Magazine, http://www.crisismagazine.com/2013/the-christian-vestiges-of-post-christianity (2013).)) If by calling our culture “post-Christian” we mean that many in our culture have experience with organized religion which associates itself with Christ and with which they are no longer involved, then “post-Christian” fits us.
On the other hand, however, those of us who advocate the Restoration Plea should be encouraged by the fact that Western culture has never been widely, truly Christian, because it has never been generally committed to following the pattern of the New Testament (e.g., Romans, 6:17). Thus, there is an enormous category of people in the West who, having perhaps known and rejected something they thought was true Christianity, have in fact never understood true Christianity. The Restorationist’s challenge is helping them to see that they made a mistake—not in rejecting a poor facsimile of the true faith, but in thinking that the facsimile was the real thing.
