Religion
Religion refers to the system within which groups of people express spiritual beliefs, values, and customs. Often this involves beliefs in one or more gods, but not always.
Many communities in the Fifth World have developed their own religious beliefs and customs. Many still consider themselves Christians, Jews, Muslims, Hindus, or Buddhists. These names, like the names of the revered figures in their belief systems, have not changed even when the content of the religion has changed drastically. Like so many other parts of the Fifth World, religions show enormous continuity and change simultaneously. Holding to the outward appearance of orthodoxy proved important as the ethos of the religion shifted so dramatically to fulfill the needs of human survival.
#Animism
If considered a religion, then animism must count as the world's oldest by far. In fact, for over a million years it would have stood as the only religion in the world, remarkable both for its religious unanimity and unsurpassed length. However, it does not seem at all clear that we can rightfully call animism a religion. Its central tenet — the recognition of personhood in other-than-human beings — can co-exist with nearly any other religion. Even at the height of civilization’s dominance, animism may have remained the largest “religion,” since most of its practitioners would have considered themselves Christians, Muslims, or Buddhists, despite their animist beliefs.
In the Fifth World, animism has become a nearly universal belief, though whether or not one can consider it a religion remains as dubious as ever.
#Christianity
Many communities in the Fifth World consider themselves Christians, though their form of Christianity may have startled their ancestors. Fifth World Christians often interpret the Fall as the story of how civilization arose, pointing to how God explicitly cursed Adam with agriculture. They point to God calling Abraham out of the only civilization in the world at that time, and how he tried to convince the Israelites not to establish a monarchy like their neighbors. They find a common thread in Christ's teachings of opposition to civilization, and often see Christ as either a patron of wizards or a wizard himself. Sometimes they even interpret the crucifixion itself as some sort of magical ritual of cosmic importance.
They often associate the collapse of civilization with Christ's Second Coming. As God created Adam and Eve in the Garden of Eden as hunter-gatherers, the end of civilization returned humanity to its original Edenic state — or at the very least to a primordial, worldwide garden.
#Islam
Imams in the Fifth World achieve their position by memorizing the Qu'ran in the original classical Arabic and successfully reciting it, word for word, to another imam's satisfaction.
Muslim communities follow sharia, though their understanding of it may not match the interpretations of imams from generations past. Those communities which could find an interpretation of sharia consistent with the ecological demands of hunting and gathering or gardening in the Fifth World survived, while the most rigidly orthodox communities did not.
Those that did survive often turned to verses like 6:38, which says, “There is no creature on earth or any bird that flies with its wing, except [they they are] a community (umma) like you.” This allowed for a fairly easy way to join Islam and animism. These communities already understood that as persons, some humans become good Muslims and some don't. They easily extended this to understand that other-than-human persons could become good Muslims or not.
#Hinduism & Buddhism
Neither Hinduism nor Buddhism needed to change much to serve the Fifth World well. Buddhism's teachings about impermanence, in particular, proved immensely well adapted to the turmoil of the Rusting Ages, though the First Noble Truth has become sometimes difficult to expound in a world that most people consider paradise.
#Judaism
With the strong social bonds that helped them weather persecution for centuries, Jewish communities often formed fared well through the turmoil of collapse and its aftermath. Like Fifth World Christians, Fifth World Jews interpret the Fall as the rise of civilization. One widespread debate among Fifth World Jews asks whether the Moshiach came and brought about the collapse of civilization — and so they should understand the Fifth World as the messianic age — or whether he still has yet to come.
Jewish communities go to enormous lengths to preserve the Torah and the Talmud, and this has made them some of the most literate people in the Fifth World. Rabbis must memorize the Torah word for word and prove themselves by reciting it to another rabbi's satisfaction.