I have been accused of this before and at first was hurt because I felt like they didn't know me. I think really it is that for them, defining identity is a big part of who they are. It's the difference between being an individual and being an individualist, maybe. So, they rightly see that I lack something they have. But I don't think I actually lack the thing they think I lack. I'm confident that I know who I am so that quest is not one I pursue. For other people, the pursuit of identity is part of who they are. They are always kind-of "finding themselves." I don't know whether this actually belongs to one cognitive function type versus the other.
I've thought about this. Ni is a dominant function quite unlike any of the others -- even Ne, which is still, as hard as it may be to believe if you've ever been around ENPs, more stable. Ne is still grounded in the objective outer-world, -- sort of like an enhanced Se, from the Intuitive perspective -- whereas Ni detaches itself completely.
When I think of an INJ, I think of a person who lives his/her life standing on an ever-shifting bit of ground, like swiftly-moving quicksand that never swallows them up, or a giant rubix-cube-thing where the colors are always being moved around, but that they never fall of off. I don't think any other type quite lives this experience, and it would probably even be terrifying for many.
So, as to the bold, I think it might not be a sure
knowing of who one is, but rather an awareness and serene acceptance that it's impossible to know and hold onto it, or that there probably isn't really a self as the others conceive it. So in relinquishing that sense of self, you actually gain it, and those constantly seeking it out are none the wiser about it for it. It's kind of like...the self is so elusive and fluid that people who are trying to hold onto it find it always just slipping out of their reach, like that stale old metaphor of water through the fist.
Predictable really, but I was reading a bit on Eastern religions in the last week, and I came across something on the conception of the universe in Hinduism...in the West we operate largely on a mechanical model of the universe, even people who are atheist or agnostic, but apparently Hindus think the universe is just God acting. So God is everything we see, including ourselves, so we're never really ourselves, we're just God acting as ourselves. So once you stop trying to be yourself, then you can be yourself. It's an entertaining and interesting notion...but you can see how INJs are in an advantageous position to align themselves, in experience, with it.