The reason I want to convince you to entertain this notion is that an awful lot of energy gets wasted by arguing against religious beliefs on logical grounds, pointing out contradictions in the Bible and whatnot.

LessWrong isn't a place that spends a lot of energy on arguing against religious beliefs. I don't think it makes much sense to copy every article from Intentional Insights to this place (even when Gleb isn't doing it himself) if the article is written for a different audience.

Spiritual is a word is a variety of different meanings:

1) Refering to the 5th element, spirit. That thing that goes around in circles. Planets move in circles around the earth because they are made from it. I think angels are also supposed to made from it. That notion of spirit also means that astrology is about spirituality when it's not about alterned state of consciousness.
2) Refering to sacredness. A value that's not tradeable with money. Moral beliefs are that way. But the Iranian's belief that Iran has a right to their own civil nuclear program also belongs in that category.
3) The feeling of being connected.
4) Deriving knowledge from intuition.
5) Epoché.
6) Surrendering.
7) Marveling at the greatness of the universe
8) Dealing with an immortal soul that distinct from our biological body and lives on after we die.
9) Feeling states of bliss
10) Things having meaning 11) Getting visions

If you want to write for LW, define your terms. Don't argue with vague notions but be specific about what you are arguing for.