Post-Christian can be defined as: the culture that emerges as the Christian faith loses influence in a society that has been somewhat shaped by Christian values. The Western world is fast becoming post-Christian and popular culture has little understanding of Christian concepts.
Take sin for instance. I can’t recall ever hearing the word sin in a secular movie or TV show. It’s not used in everyday conversations. It seems to not exist in a post-Christian environment.
However, moral standards come downloaded into human hearts as standard equipment. This sense of right and wrong is called the conscience. The human software of conscience doesn’t come from nowhere, it has a source — the living God. God’s commandments are also recorded in Scripture.
To violate God’s moral standards is sin. They are universal, even if we deny them. Sin separates us from God (this is spiritual death). It leads to gradual (or sometimes rapid) self-destruction and misery. It also produces guilt which people often try to ignore or deny. However, even if denied, guilt, like a cancer, eats at a person’s emotions and causes feelings of alienation from God. This isn’t just theory, it is lived out in our day-to-day lives.
Christianity proclaims that Jesus came to save us from our sins, to set us free from bondage to wrongful desires and behaviors. Jesus called on people to repent, to stop their sins and to begin to engage in morally right thinking, talking, and behaving. He gives us a desire not to sin, a desire for His will rather than our own.
In Christianity we are called to stop sinning — to turn away from self and its cravings and to align ourselves with God’s morality. In a post-Christian world, people align themselves to their own desires, opinions, or feelings and then proclaim themselves to be good people, thus calling sin good.