This trope is quite important in Douglas Adams’s The Long Dark Teatime of the Soul, part of the Dirk Gently series. But note that the number of believers or worshipers is not directly correlated to the gods power levels. It’s more about vague ideas that get collected into the personification of a god. Worshipers help, but only because they are deliberately thinking about those ideas that make up said god. And said gods are still immortal, even if they are effectively powerless.
It doesn’t help that Odin – “the chief and fount of all the power of the Norse gods … The one all the others depend on for their power” – has sold his soul to some unscrupulous mortals shortly before the story opens; the big guy is thus getting restful VIP treatment hereabouts while the rest of the Norse deities suddenly and explicitly find themselves dealing with lowered power levels.
‘I refuse to prove that I exist,’ says God, ‘for proof denies faith, and without faith I am nothing.’
"‘But,’ says Man, ‘the Babel fish is a dead giveaway, isn’t it? It could not have evolved by chance. It proves you exist, and so therefore, by your own argument, you don’t. QED.’
"‘Oh dear,’ says God. ‘I hadn’t thought of that,’ and promptly vanishes in a puff of logic.
I know I read a short story in an anthology sometime ago: A god of fish went into a kind of “waiting room”, where he meets older gods who are being repurposed into other human type lives (I think some of the Norse gods are going into a circus or a theater). The reason the old gods are in the room, he learns, is people are not beliving in them any more, they have moved to a new god. The fish god is happy because fish always belive in him, fish don’t learn about other gods, then he realizes that if he is in the room them fish must have stopped believing in him. At the end Jesus come in because there is a new god LL. I am sorry I can’t rememeber the name or author. I am pretty sure I read this before I read any Pratchett.
Yeah, but that’s a bit more spoilery than I wanted to get. I guess I should have mentioned it obliquely, though. Like just saying that Odin had done something for himself that lowered everyone’s power levels.
I might have missed it (although I did a search on both pages of this thread), but it seems to me that this trope can hark back to Barrie’s Peter Pan and the whole “Clap if you believe in fairies” bit in the stage play. Earlier in the play Peter tells Wendy that when people say they don’t believe in fairies they get weaker. Not a big step from fairies to gods.
Aside from Peter Pan, the first time I recall seeing the idea was in the aforemention Star Trek TOS episode with the Greek Gods. But I’ve envcountered the idea quite a bit in older fantasy, even if most people’s familiarity with it is from more recent works.
Kipling’s 1906 Puck of Pook’s Hill lines up with Barrie’s works so I’d guess it goes even further back.
But since I was looking “They were always landing in those days, or being driven back to their ships, and they always brought their Gods with them. England is a bad country for Gods.”
I can’t believe I didn’t mention P. C. Hodgell’s Godstalk before, given that it’s my favorite novel. The story actually beings on the night of the Feast of the Dead Gods, the one night each year when the gods that have faded away for lack of worshipers return to the city to feast on sacrifices…which is to say, whatever they can catch.
Later, the protagonist accidentally kills a god by breaking (temporarily) the faith of his last priest, who was also the god’s last worshiper.
The concept comes up in a few of his other stories also with respect to the Street of the Gods in Lankhmar. Various temples and gods move up and down in prominence on the street according to their popularity with worshippers, and the gods’ power correlates with that popularity.
The oldest use of the trope in fiction that I can think of is Robert E Howard’s Conan story Twilight Of The Grey God. The last tribe believing in the titular deity is wiped out in battle. So, he ceases to exist.