It is a brilliant question - perhaps the only question. Buddhism - particularly Zen Buddhism this is essentially the only inquiry. The Greeks spent much time with this and expounded many ideas - your question has some of the flavor of a Socratic Dialogue. Many, many Philosophers have spent their entire lives working on such a question; The Existentialists, Camus, Kierkegaard to some degree - in fact - I'm gonna go out on a limb here and say that any philophy that devlves into human discourse,thinking,emotion,action,etc. is fundamentally only finding new ways to ask this question. So you're not alone.
Moreover, given the proliferation of great minds who have dedicated themselves to this, it seems unlikely that someone will provide some new conclusive answer in a StackExchange thread - just saying. But, what is possible is that someone can offer up a view - a way of looking at the question that gives whoever reads it a new thread to pull at while investigating the question for themselves.
No One's Mouth Is Big Enough To Say The Whole Thing!
So I have no intention of trying. One way to look at this question is - without dwelling upon the origins of this phenomenom - is that we have a broken (at best constrained) way of thinking, because we have a broken/limited way of talking. Our speech has trained us to relate to the world in such a way that all action must have an actor - anything existing must follow from that which gave it existence - and we give everything an origin and forget that we have done so. No matter how absurd we recognize our notions to be - we as a species are anchored to looking at the world from the perspective of the way our language is constructed.
The "Doer" flaw is everywhere - not just in relationship to the "I" illusion, but in relationship to everything with which we interact. Examples:
- It is raining.
- It has been a rotten day. (It has?)
- The Waves are thrashing on the beach.
etc. Those were just a few hasty examples, but they illuminate our confusion.
Something else that is an interesting corrolary in the field of social psychology is the fundamental attribution error.
[The fundamental attribution error] is people's tendency to place an undue emphasis on internal characteristics to explain someone else's behavior in a given situation, rather than considering external factors.
The flip side of this error is the actor–observer bias, in which people tend to overemphasize the role of a situation in their behaviors and underemphasize the role of their own personalities
As a simple example, consider a situation where Alice, a driver, is about to pass through an intersection. Her light turns green and she begins to accelerate, but another car drives through the red light and crosses in front of her. The fundamental attribution error may lead her to think that the driver of the other car was an unskilled or reckless driver. This will be an error if the other driver had a good reason for running the light, such as rushing a patient to the hospital.
Consider how we use language to slice the world into abstract objects we see (we don't consider ourselves objects). We might interact with another person for a day, and say to ourselves "I don't like him"; and say it so fast we almost don't realize we have done it.
We mostly don't stop to think about what we've done:
1. We have placed judgement on a person as if he were a thing that was and will always be only that way.
2. We've assigned ourselves omniscience of perspective - we can correctly assess a collection of personal impressions formed rapidly about this peron; come to the right conclusion about what they mean; and then convert them into traits that dictate who that person can and shall be.
That's just the tip of the iceberg. But, what's most fundamental is that you only know who that person is when he's being who he be's when you're there.
Said another way. You only see him as he occurrs while he is in relationship with you. Perhaps you get shy, because you think he is being mean to you. However, you grant him not that same opportunity. You are effected by him as he is an
it in the world, and
it affected you - you know, like when
We also grant him - as we do to some degree all
its - a sort of omnipotence of intent. In other words - the way he is is something he is completely in control of and at the source of - and his motivations for the way he was being were something he way completely in control of and we're completely clear to him.
And here is one place where language solidifies things. What happened was merely a moment - moments; maleable seas of experience wherein the mind latches on to one particular notion - or one context - and gave that particular context solid existence that can now be distinguished from other parts of existence. The problem with this is that everything is in motion at all times - there is no "one way" that things happened that day any more than there is one permanent anything. Praise Hereclitus (sp?) for saying:
It is not possible to step in the same river twice.
Any reference to the self in language is always a reference to a particular sensaton, emotion, state of being, thought, memory etc. Our language transforms fluid sensations into solid sates, TRUTHS, preference,etc and then promptly forgets that it has done so. Things like "I am funny" or "I don't like her" are merely frozen thoughts that have been sitting around and examined and polished over time. There is nothing to point to.
And still this is just the tip of the tip..But it's enough now. No one can offer an answer to the question "What Is I?" But what almost anyone can do if they deliberate for just a second or two is to point to "What Is Not I". Maybe mastery in the game called - being aware of "What I is not" - leads to something like seeing "What I is".