Please note: I get a little harsh in this piece. Be forewarned.
You've almost certainly heard this trope:
It doesn't necessarily mean that the person is woo (although it often does). People use it who hold more or less traditional theistic beliefs, but have left their organized religion or never belonged to one. (For those people, the trope often goes, "I'm not religious, but I worship God in my own way.") People use it to mean they believe in something other than the physical world: they don't know exactly what, but they're pretty sure it's something. People even use it to mean that they find some sort of meaning and transcendence in life, and don't know another word or context for meaning and transcendence other than spirituality.
But I don't think unorganized spirituality holds any more water than conventional religious beliefs. And while it doesn't have the same power to brutalize or oppress that traditional organized religion does, it does have much the same power to derail critical thinking, and to prioritize personal bias over evidence, and to base important decisions on a foundation of sand.
Now, when I'm in a generous mood, I see this trope as coming from a totally valid desire to not be connected with the horrors of organized religion... while, at the same time, still feeling some sort of personal, emotional experience that the trope-holder thinks is a connection with God. (Or the Goddess, or the spirit world, or whatever.) The people who say it are trying to separate the wheat from the chaff; to take what they need and leave the rest. And while I think their interpretation of their experience is mistaken -- I think it's all chaff -- I can certainly understand the impulse.
And sometimes, like deism, the "spiritual but not religious" trope is a gateway drug, a baby step out of religious belief. For people who are questioning religious belief but have been brought up to believe that religion is the source of all morality and meaning, "spiritual but not religious" can be a way to begin to let go of their beliefs without feeling like they're stepping into the abyss. And I can definitely be generous about that.
When I'm in a less generous mood, though, I see this trope as totally smug and superior, without anything to back it up. I see it as a way of saying, "I am so special and independent, of course I don't have anything to do with that hidebound organized religion, I'm far too free a spirit for that... but I'm also special and sensitive, and in touch with the powerful sacred things beyond this mundane world."
So what's my problem with it? Other than the smugness, I mean?
The obvious problem, of course, is that there's not a shred of good evidence to back it up. There's no more evidence for disorganized religion than there is for organized religion.
And in my experience, "spiritual but not religious" tends to be a very sloppy form of spirituality. It lacks even the tortured rigor of carefully thought-out theology; the discipline, pointless though it may be, of fervent religious practice. All too often, "spiritual but not religious" seems to mean, "I believe in some sort of supernatural world, but am not willing to give that belief much thought, or to seriously consider whether the spiritual world I believe in is consistent or makes sense."
Rather more importantly, I think the "spiritual but not religious" trope completely plays into the idea that religious belief -- excuse me, spiritual belief -- makes you a finer, better person. There's a defensiveness to it: like what the person is really saying is, "I don't attend any religious services or practice any religious practice... but I'm not a bad person. Of course I still feel a connection to God/ the soul. I haven't totally descended to the gutter. What do you take me for?" It gives aid and comfort to the idea that value and joy, transcendence and meaning, have to come from the spiritual -- i.e. the world of the spirit, the world of the supernatural.
But I think my biggest problem with the "spiritual but not religious" trope is with the "mundane world" thing.
If being "spiritual but not religious" really does mean thinking of yourself as being in touch with the special sacred things beyond this mundane physical world... then I think that shows a piss- poor attitude towards the mundane physical world.
The physical world is anything but mundane. The physical world is black holes at the center of every spiral galaxy. It is billions of galaxies rushing away from each other at breakneck speed. It is solid matter that is anything but solid: particles that can't be seen by even the strongest microscope, separated by gaping vastnesses of nothing. It is living things that are all related, all with the same great- great- great- to the power of a zillion grandmother. It is space that curves, continents that drift. It is cells of organic tissue that somehow generate consciousness and selfhood.
When you take the time to learn about the mundane physical world, you find that it is anything but mundane.
And I think that the "I don't follow any organized religion, but I know that there has to be something more to life than what we see" is doing a serious disservice to the astonishing and complex vastness of what we see.
As a blogger or commenter somewhere whose name I can't remember once wrote: The "I'm spiritual but not religious" trope is trying to have the best of both worlds... but it's actually getting the worst. It's keeping the part of religion that's the indefensible, unsupported- by- a- scrap- of- evidence belief in invisible beings; indeed, the part of religion that sees those invisible beings as more real, and more important, than the real physical world we live in. It's keeping the part of religion that devalues reason and evidence and careful thinking, in favor of hanging onto any cockamamie idea that appeals to your wishful thinking. It's keeping the part of religion that equates morality and value with believing in invisible friends. It's keeping the part of religion that involves conferring a sense of superiority onto yourself, solely on the basis of your purported connection with an invisible world.
It's keeping all that... and abandoning the part of religion that is community, and shared ritual, and charitable works, and a sense of belonging. It's throwing out the baby, and keeping the bathwater -- and then patting yourself on the back and saying, "Look at all this wonderful bathwater I have!"