A contradicts B. You didn't oppose these convictions in your original post, but rather suggested that B is a variant of A that believers can accept. While it is a very different argument, at least in my opinion.
B itself is contradictory as claimed by you, because you claim to know something about the essence (that a non-believer can't grasp it) while claiming that you can't know it.
I didn't say that I can know nothing
about a hypothetical essence. I cannot grasp it to the extent that is necessary for me to engage with it any substantial manner, but I can know that I don't know what it is (provided it does exist). It's like saying that you don't think God exists, but you know that, if he did exist, you wouldn't be able to claim to know who or what God is. Because if you knew, then you wouldn't even be thinking that he doesn't exist. Duh!
Squonk said:
It would be contradictory if claimed by a believer also (unless he's a convert), because a believer can't tell if a non-believer gets it or not. Anyway, does your theory say that all believers know the essence, or just some of them?
I wouldn't make any claim about that. It doesn't really matter anyway.
Squonk said:
If some of them, than it quarrels with some of your other theories, because one may claim that, say, jews acting good doesn't imply there's a valid reason to think judaism can be interpreted in a good way, because we may write them off as the ones not knowing the essence of their own religion.
God, I'm not proposing multiple "theories"
Why should we write off any believer for not knowing the essence of his/her religion? What gives us any claim to being able to do that?
Squonk said:
But if we say that all believers know the essence of their religion, there are another problems. For example, that would imply that it's enough to know the essence to become adherent of such religion. One may wonder why don't the believers share this wonderful essence with non-believers so that we may all unite in their faith
They do but you just don't
get it? Duh.
Squonk said:
Moreover, knowledge about one thing doesn't exclude knowledge of another, while being a member of one religion most often excludes being a member of another. Therefore, being a member of some religion is not about knowing anything.
Don't know what this is supposed to mean. Sounds like a terrible argument. First of all, it depends on what kind of knowledge you mean - it's not humanly possible as it is to have all the tacit knowledge in the world, because that would imply that you're capable of being 'everywhere' and learning continuously throughout. So, in some sense, tacit knowledge of something can exclude that of another.
Also, if you were the adherent of, say, an Abrahamic religion, chances are you would deny that other religions possess the same
kind of special knowledge that you have. They may know more about other things than you, especially pertaining to their own religions, but you'd still claim to have access to some kind of special (divine) knowledge that they don't. In other words, you and your fellow believers are special in that particular and significant manner that no one else is - the knowledge you possess is indeed exclusive, but not because it excludes other comparable knowledge.
Squonk said:
But you've just claimed you don't believe it exists! Anyway, you claim something more about it than that it exists. You claim, on unknown basis, that only believers can grasp it. Which you'd have to prove. But which also means you know something about this essence.
Yes, I do know something about this essence, if it exists, which is that I don't know what it is. This is not contradiction. It's so basic that don't how I can make you understand this if you still can't
Squonk said:
Why? I don't see any basis for this claim.
Because they believe and you don't? There is clearly a difference between you and them, and so that, in a sense, makes them special. Of course, you can say that non-believers are special too, just in the opposite way. But it's just convenient to say that some people are special when the presence of something (rather than its absence) differentiates them.
Squonk said:
The "essence" in my opinion is quite simple. There's no god but God and Muhammad is his prophet. That's the most essential belief. but I wouldn't say they "understand it". They believe in it.
That is a fundamental tenet, not an essence. If the essence can be formulated and communicated in so many words, then the necessary difference between believers and non-believers would disappear, making the distinction obsolete. That is obviously not the case, though.
Squonk said:
What do you base your assertion that "believers think they know something about their faith that non-believers don't" on? What's the basis to think that non-believers can't understand it?
Because if you did understand it, you wouldn't be a non-believer? I'm not saying that I think there is an essence. But believers can claim that there is an essence, the understanding of which is necessarily tied to the acceptance of the faith, and that would be quite reasonable. Whether this is correct or not, there is no reason to believe that a non-believer is in a better position to claim to understand the essence of a religion, if there is such a thing.
Squonk said:
Anyway, as I've mentioned, I do not think that being a member of a certain religion is about knowing something. One may say "I know Muhammad is a prophet" or "I know RCC was founded by Jesus, the Son of God", but it's a belief, not a knowledge. Believers may regard it as a knowledge, but it's not.
So you're saying religious belief has nothing to do with knowledge? Sounds like fideism to me.
Funnily enough, you've been studying Islam in some capacity, and yet you claim that being a Muslim is not about knowing something. So what's the point of Muslims reading and studying the Quran, then? I don't know whether it's just you or where you learned what you know from.
Squonk said:
I wouldn't want such a teacher anyway. I take your responce as a sign of not being able to defend your wrong ideas.

Suit yourself.
Squonk said:
Isn't that obvious? The prophet was still alive, he looked upon people and could correct them if he though (God thought) they were doing something wrong. Also, people of that day, at least the ones around the prophet, knew more about his (or God's, if you believe he was a prophet) ideas than we do today. Not all coranic verses were saved from being forgotten. Not all words of Muhammad, or actions, are recorded. They knew more about what he expected them to do, and they were corrected by him if they didn't do it right.
The original praxis was ordered and accepted by God through his Messenger. That's what makes it purer from non-religious influences than the one existing today. Fundamentalists are often "right" in their beliefs. You believe the more liberal fractions are right, because it suits you. I don't give preconditions to whom I find interpreting something right.
So, in other words, you think that Salafism is the "right" brand of Islam. And you want to be able to generalise about Islam and all Muslims from your knowledge of it. Wow, just wow.