What's the name of a classic sci-fi short story about a planet where their religion makes people willingly merge with a parasite in a cave and die?
Outsiders can't understand why anyone would do such a thing, and when off-world visitors start joining the religion and committing suicide, two humans (a couple) with psychic abilities are sent to get their impressions.
They discover the reason everyone happily merges with the parasite is that, by merging (and slowly dying), in return they join a joyous mental community of every previous person who has joined, with overwhelming feelings of happiness--ecstasy, really.
All the psychic love is nirvana for the very sensitive female partner. She joins the religion and merges. She asks her partner to join the parasite as well but he refuses.
The male leaves the planet with the realization that their love for each other couldn't compete with the parasite-mediated mass love and happiness on the planet.
After finishing the story it brings up thought-provoking ideas on whether you would join such a community, about the ties of your love to your own family,and does organized religion gain our interest by similar promises of eternal happiness?