There's a middle-aged couple who run the dry-cleaners down the road from me. In the past I've been a regular there, financial jobs like mine having a high formal-suit quotient. So I've got to know them quite well.
They're lovely people. Immigrants from Rajasthan (largest state in India), they've been over here a couple of decades now. They're really friendly and always make me feel welcome.
They're also quite religious. Once upon a time that would have been a problem for me, not because it bothered me but because it would start me ranting. I'd debated the God question online for so long that the thread of the argument had burned its way into my brain. In recent years I've been trying to train myself to resist this compulsion.
So when we started chatting about it, I did my best to shut up and listen. And what I learned was quite interesting to me. I've always been fascinated by small religions, and this couple are both passionate about one I hadn't ever heard of before, called "Santmat" (roughly: the way of the saints).
Santmat is a classic "medley" religion. Just as Sikhism originated in an attempt to meld Hinduism with Islam, Santmat claims that each of these groups has an equally valid handle on the truth. In particular, they each have genuine gurus, or saints - individuals in whom the spark of the divine burns most strongly.
In the usual three-blind-men-and-an-elephant fashion, these saints all perceive the same divinity, but interpret it to their followers in a way that is appropriate to the time and place in which they operate. Saying that one religion is truer than another is nonsensical; if each has a true saint at its heart, they are just as valid. If you don't find one religion convincing, that just means that you're not destined to become a follower of that particular guru.
For this reason, I'm not entirely sure that Santmat can be considered a religion in the normal sense. It's more a philosophy, a system for putting all the other religions in context. The part that does count as a religion is the Radha Soami Satsang Beas, which is a group formed around a particular lineage of saints.
Each of these gurus made more converts for the Radha Soami movement. The sociology of this is interesting. You must remember that in Santmat, the important thing is the saint you follow rather than the name you call your religion. So followers of each guru tend to see themselves as distinct from the other "waves".
For example, my friends from the dry-cleaners were converted by the guru Maharaj Charan Singh Ji. Although he passed away in 1990, I think they feel a stronger affinity for him and his "generation" of believers than they do for the current guru (Baba Gurinder Singh Ji, Charan Singh's successor). Certainly the religious literature they've been feeding me seems to focus on him. There's no acrimony; your choice of guru to follow is as personal as your choice of woman to fall in love with, and people aren't expected to have the same preference.
Generally a rather nice, innocent religious group, with no blots on its history. So do I find them convincing? Am I going to find a guru of my own?
Unsurprisingly, the answer is: probably not. Firstly, of course, I find their cosmology unconvincing. I don't see any particular reason to believe that we have souls, for example.
The Santmat rebuttal here is: I don't believe in souls because I listen to scientists; they do believe in souls because they listen to saints. We've just chosen different gurus.
But this misses the point. In short: how do you choose a guru?*
The Santmat approach is your basic touchy-feely "you just know he's the one" kind of thing. But this is a problem for me because, back in the material world, many people have felt like that about some very scary characters. Hitler was considered quite the role model at one point, as was Stalin (still is, in some circles).
So, in situations where we can test how good people are at picking good gurus, we find the answer is: not very.
But that's kinda nihilistic. If people are bad at choosing trustworthy gurus, how do I know my scientists can be trusted? After all, there are some scandals in the history of science too (cold fusion, Hwang Woo-suk's cloning research, I could go on all day).
The answer is nicely paradoxical. I trust the scientific community because I don't have to. They don't expect me to. When they tell me something, they also present me with the data to back it up, and the method that gave rise to that data, and I can go away and confirm it all for myself.
By and large I don't bother to check the data - it'd be very time-consuming and expensive. Fortunately, there are lots of other scientists who are generally willing to replicate experiments, especially interesting or controversial ones. Scientists keep each other honest.
I don't see any evidence that gurus have that kind of skeptical mindset. Until I do, I won't be believing in souls.
* I should mention that this question is explicitly raised in one of their books (ch2 of The Science of Spirituality). Sadly, I don't think they actually answer in plain language. As far as I can tell, the chapter just boils down to: you'll know him/her when you see him/her.