In my world - as in the real world - there are accounts of the gods walking alongside mortal men. They tutored mankind, fought with mankind, and bred demigods with mankind. This is accepted as an actual part of factual history as well as religious history. The world has entered into an enlightened age. As time went on, the gods grew more and more distant until they stopped appearing all together. So. I have a few questions.
1 - Is it reasonable to assume that organized religion would grow stronger in the absence of tangible gods? In my world, there aren't any religious texts from the time that the gods walked among men. All the accounts written at the time are secular. The prominent religious texts are relatively new and were written a few hundred years after the gods stopped appearing before mortals .
2 - Is it reasonable that their return wouldn't be seen a frightening event? Obviously this is something hard to compare to real world religions since many of them speak of their deities returning at the end of the world and so on. But given that there is no such link between the gods returning and the world ending, would it be safe to assume that while people would treat the return as the largest event in history, no one would freak out too much? I had the idea that most people would assume that they'd finally done something right/ finally proved themselves worthy of having the gods return. People would fall at their feet, but the world itself wouldn't go to pieces, would it?
3 - Is it safe to assume that faith and religion would be separate for a legitimate portion of the population? Not everyone follows religion in a hardcore way because some feel that organized religion isn't necessary since it wasn't something the gods asked for while they were in the world. They asked for worship and respect, but not the pomp that the religion in the fantasy world offers. Most people are spiritual in some way. Ghosts are commonplace. Spirits are rarer but still something that most people will encounter at least once or twice during their lifetime. I've made the distinction that "ghost" refers to dead mortals, while a "spirit" is a genius loci. The existence of ghosts and spirits is accepted - by some people and stated outright in religious texts - as proof that the world is not mundane and that there are realms beyond this one. This can't be proven because ghosts themselves know nothing of the afterlife as they haven't crossed over into the afterlife yet and can't come back once they do. Spirits don't think in the same way that mortals do so communicating with them about the afterlife is impossible as they don't comprehend the concept.
4 - Is it likely that several different branches of the religion would pop up over the years despite all of them believing in the same gods? In our world we have - according to Wikipedia - 41,000 branches of Christianity alone. Granted not all of them are major, but it's still a staggering figure. I'd assume that I'm not unreasonable in thinking that such things would occur in my world as well. The major Abrahamic religions are vastly different from one another despite Abraham himself being important to all of them so I'd guess that I'm not wrong in assuming that entirely different faiths would pop up as well.
5 - Magic and science are both codified. The world is going through an enlightened phase. The scientific method is being applied to the world in general by some academics. They feel that the accounts of gods are just stories and can't be proven. Some feel that the gods were simply magicians in an age where magic was rarer and thought to have divine origins so a powerful magician could seem like a god to uneducated people. They also feel that ghosts and spirits are a natural part of the world that goes along with magic, rather than being indicators of divinity. Is it fair to assume that there would be a growing amount of atheists? This wasn't uncommon in our world either, even during the time period, but it wasn't exactly widespread either.
6 - How would this affect the government? The gods have no intent to rule, but would their presence erode governmental power or strengthen it? The government is an odd hybrid of the British system with bits of the Holy Roman Empire.
Search terms used: incarnations of gods, gods walking among men, return of the gods
Of course this is a difficult thing to search for so all of my results dealt with the real world faiths and the results were mainly about Christianity.