How so? Isn't it just realizing that in being part of everything, you are everything?
If so then it really supersedes any sense of self.
It's always the same with CHIM threads. At one point, there will always be one (who thinks who knows exactly what it is) who spoils what it is. And then it leads to total confusion. Because the one asking mostly neither has the background nor the knowledge to understand its meaning. (And too often, the one who spoils it doesn't really understand it either.)
Telling what CHIM is to someone who didn't put at least a little of his own research in it is like answering the question "Excuse me, Sir, but where am I?" with "Here". The answer might be correct, but it doesn't help the one who poses the question.
So, to the thread starter or anyone who wants to know about CHIM: do a little work for yourselves.
Here are a few pointers for the start:
Have a go at the Sermons and read them. Read them, don't budge out in the middle because you think it's gibberish. Read them again just to be sure you get a feeling for the language and the text itself.
While reading, try to answer the following question:
To whom are these texts adressed?When you can answer above question, ask yourself why Vivec specifically chose that adress. Also, keep in mind that they are titled "Lessons", so they are meant to teach something, besides being poetry.
Another little hint that I hope might make things easier: when you come across seemingly overly complicated passages. A lot of Vehk's Sermons are metaphors for things that are undescribable for most readers. Imagine someone never having seen or heard of snow before and you have to describe it to him. You can't just say its snow, because he wouldn't understand it. Maybe you would say something along the lines of "it's like white, cold down falling from the clouds".
Vehk's doing exactly that. Describing the "indescribable" in words that can be understood.
Then, take Vehk's Teachings, they elaborate on the Sermons. Also, the Loveletter of the Fifth Era is an important thing to read. Keep in mind, CHIM in itself is - once you figure it out - not a very complicated thing to "know" - anyone can do it and even have it without even knowing. Including you. The greater meaning of it - for Tamriel et all - and thus the fascination, reveals itself when putting thought into it. And noone can think for you, you just have to do it by yourself.
Oh, and as for the original question, no, when you do all I said above, you won't know what CHIM is - but you might be on the way. And you will have some ground to walk on once you take the next steps.