Question: "What does it mean for a society to be post-Christian?"
Answer: The term post-Christian has no universally accepted definition, though it is often applied to modern Western cultures. In that use, a post-Christian society is historically based in Christian ideas and follows simplified Christian values, but rejects the authority of Christianity and does not consider it the basis of either its ethics or its culture. The Christian language and expression that once permeated society become rare or superficial in a post-Christian society. In contrast to other cultures that are explicitly anti-Christian or grounded in a different religion, such as Islam, a post-Christian society selectively claims virtues rooted in a Christian worldview, while selectively rejecting the truths that make those values possible.
The change in society is not necessarily about identification: a large proportion of those exhibiting a post-Christian worldview may still identify themselves with the term Christian. Labels do not replace reality, however (2 Corinthians 13:5). Many self-identified “Christians” in a post-Christian society lack basic knowledge of biblical faith. Prior generations took such knowledge for granted; its absence widens the disconnect between the culture’s assumed values and its self-perception. Fading understanding of biblical faith, ironically, sometimes leads people to think they “know better” than their spiritual predecessors (see Proverbs 15:5).
A common thread in post-Christian culture is the assumption of Christian values without respect for Christian contributions. That which is perceived as “good” is assumed to be self-evident, despite having Christian roots. Restrictions that conflict with evolving desires are assumed to be frivolous, despite having prevented disaster in the past (Proverbs 13:14). In truth, most distinguishing values of Western culture—both positive obligations and restraints—are natural only to a Judeo-Christian worldview.
Prior to widespread acceptance of Christianity, the values taken for granted in post-Christian cultures were virtually nonexistent. Human equality, gender equality, the fallibility of human government, and charity as an obligation were all unknown in pagan cultures such as ancient Rome. Pre-Christian sexual ethics emphasized the inherent right of the strong to take advantage of the weak. Slavery—contrary to common myths—was widely opposed by early Christians and eventually abolished only through efforts grounded in a Christian worldview. The scientific method itself is rooted in assumptions found only in theistic views and developed only when Christianity became prevalent.
Post-Christian societies claim values derived from Christianity, such as equality and charity, while denying that those ideals are inherently Christian. At the same time, a post-Christian society undermines aspects of the Christian worldview that interfere with its evolving preferences (2 Timothy 4:3). As consequences for those choices mount, it’s common for a post-Christian society to blame prior generations and prior beliefs rather than acknowledge the truth (see Romans 1:21–31).
Superficially, eroding reliance on Christianity makes it easier for a post-Christian society to justify things condemned by a biblical worldview. However, this also dissolves the fundamental basis for positive values that society wants to claim. As a result, post-Christian societies begin to blur—or outright ignore—boundaries regarding human rights or charity. Abortion and “mercy killing” are examples of this perverted upending of ethical ideals.
The loss of transcendent foundations also leaves a post-Christian society struggling to justify its preferred ethics (Jude 1:12–13). Where such a culture used to point to God and the Bible as reasons for certain actions, it now points to some vague version of “just because.” That vacuum cannot last, of course, and so most post-Christian societies begin to replace the authority of God and the Bible with the authority of the state or popular opinion. The concept of moral responsibility takes second place to legality, loopholes, or mob justice (Mark 7:8).
Eventually, a post-Christian society moves from assuming Christian values to ignoring them, to resenting them, to repressing them, and eventually to persecuting them. What was once Christian and is now post-Christian will eventually become anti-Christian. Where any specific culture is in that process is subject to debate. No two cultures are exactly the same. In all cases, believers and skeptics alike ought to recognize the dangers inherent in dissolving Judeo-Christian ethical foundations (Matthew 7:26–27). Restoration is possible (Psalm 80:3; 1 Peter 5:10) but not apart from the Holy Spirit’s intervention (John 16:8; Jude 1:17–23).