It would be ideal if theists would participate here ...
It doesn't take a theist to answer this question.
But the question is whether that kind of supposed theism, actually is theism - or is it theism only in name, but not in actuality. Perhaps such theism is merely an empty shell, a puppet.
How so? Theism is simply the belief in god, so if she believes in god, she is a theist.
That doesn't mean they have it.
You could say the same about anyone, including the founders of major organized religions.
Sure.
The point here is, though, as noted earlier:
If all the information that humans can possibly have about God necessarily comes via other people (as a common theistic reasoning goes), and these people need to be part of a theistic tradition for that information to be valid, then those outside of that tradition are cut off from knowledge about God.
But that's not an accurate statement, because information about God purportedly comes from God himself. That's what revelation is, and all the major monotheisms rely heavily on it. It often is disseminated by people, but that's clearly not the only place from which the faithful claim to get their information. Each person holding their own, independent interpretation of God could very well claim to have gotten that concept from God himself. (Or "the gods," should they be polytheistic)
I'll put it this way:
Imagine trying to be a theist on your own, without adherence to any particular theistic tradition.
Unless you get very fortunate and God blesses you with divine revelation, you will be left to ecclecticism and your own imagination. And unless you are extremely comfortable with idiosyncrasies, your own deliberate eccelcticism and making stuff up are going to start to bother you, and you will also notice that being alone in your beliefs is alienating to the point of making you dysfunctional.
Except that's not what happens. Most people who claim to believe in God without all the church business don't tend to be overly pious or even stringent, precisely because there is no dogma to follow. This is why I say modern Christianity has become more of a spiritualism than a dogmatic religion; churches are closing their doors because nobody's showing up, but we still have millions and millions of self-identifying Christians in the country.
The people who
do break off from organized religion, and sort of cook up a dogma on their own, end up founding splinter sects. Christianity itself is just a weird Jewish cult, and under its umbrella are a bunch of other weird splinter factions, such as the Mormons or the Evangelicals.
Being a member of and drawing on a traditional religion, you have a referential community in relation to which your theism can meaningfully function and be communicated. Even if currently you aren't a member of a particular church, you have a sense that you belong somewhere, on principle.
There are certainly benefits to being in a group, and no doubt that belief in something is strengthened when you're surrounded by a bunch of like-minded individuals. I would not say, however, that the lack of these luxuries inhibits belief. We see too many examples of people who believe in a version of God that suits them to say that the absence of a church or a faction lessens that. I just don't see it.
On your own, you don't have that, and your theism is more like a mere dead accessoire that you drag around with you. On your own, you know that you don't belong to any church, that you are alien to all other people who call themselves "theists."
You know, I'm sure people do feel that way. I'm sure there are people who truly believe but feel like something's missing. That said, I don't think not having a church or a particular denomination matters all that much to most people. Nor would I say that not having one makes you alien to people who do. I mean, I'm an
atheist, and I'm no social pariah. My believing friends--even my religious friends--don't feel a disconnect with me, nor I with them. (I will say, though, that the more pious one is, the less likely I am to suffer them, but I'd like to think I'd feel this way even if I was a believer; I'd be the Pope rolling his eyes while people dropped to their hands and knees in front of me.)
But really, even if it were true that people felt this way, it still wouldn't make them any less of a theist than someone who goes to Temple every Friday.