Christian existentialism is a theo-philosophical movement which takes an existentialist approach to Christian theology. The school of thought is often traced back to the work of the Danish philosopher and theologian Søren Kierkegaard (1813–1855), who is considered the father of existentialism.
Christian existentialism relies on Kierkegaard's understanding of Christianity. Kierkegaard argued that the universe is fundamentally paradoxical, and that its greatest paradox is the transcendent union of God and humans in the person of Jesus Christ. He also posited having a personal relationship with God that supersedes all prescribed moralities, social structures and communal norms, since he asserted that following social conventions is essentially a personal aesthetic choice made by individuals.
Kierkegaard proposed that each person must make independent choices, which then constitute his existence. Each person suffers from the anguish of indecision (whether knowingly or unknowingly) until he commits to a particular choice about the way to live. Kierkegaard also proposed three rubrics with which to understand the conditions that issue from distinct life choices: the aesthetic, the ethical, and the religious.
One of the major premises of Christian existentialism entails calling the masses back to a more genuine form of Christianity. This form is often identified with some notion of Early Christianity, which mostly existed during the first three centuries after Christ's crucifixion. Beginning with the Edict of Milan, which was issued by Roman Emperor Constantine I in AD 313, Christianity enjoyed a level of popularity among Romans and later among other Europeans. And yet Kierkegaard asserted that by the 19th century, the ultimate meaning of New Testament Christianity (love, cf. agape, mercy and loving-kindness) had become perverted, and Christianity had deviated considerably from its original threefold message of grace, humility, and love.