Very few challenge this fundamental belief. Even those in spiritual circles that claim to be practicing towards "unity" never really challenge this belief. The idea that we are all somehow one is accepted (obnoxiously celebrated), everyone does their practice, and then they go about their day perpetuating their conscious and unconscious belief in a separated and disparate reality. This is all, of course, suffering and insanity.
When I sit down with someone that is serious about truth (and not just interested in playing spiritual) and we challenge this fundamental assumption, it normally dissolves in about 10 minutes. The longest it took is 45 minutes. The quickest was 15 seconds. But the most important thing is that it always falls away, because separation is not reality. Separation is just a perspective within a reality. Unity is also just a perspective within reality. Awakening is not dissolving separation into a permanent state of unity. Permanent states don't exist, and to believe that freedom is always feeling a warm and fluffy state of unity is, at best, annoying.
Freedom, awakening, or enlightenment (I use these terms interchangeably), is the whole fucking thing. Yes, that's right, everything.
When you challenge your sense of separation, you can see that there is no real boundary. You can do this right now: where do you end and everything else begins? If you rely on your vision, you'll probably look down and think, my body. Okay, interesting, does it feel like you end at your body? Feel for a second. I would imagine that you either feel bigger or smaller than your body. Now that's interesting, isn't it? I would also imagine that, unless you feel like everything in your experience is you, that this feeling sense of self is moving like a tide, pulsing. Changing. Isn't that interesting?
Now taste. Yes, taste. Taste yourself. (I Don't mean lick yourself, that's gross. I mean taste.) When you taste, do you feel like you're only what you're tasting, more than what you're tasting, or not what you're tasting? When you really focus on taste, notice what happens to your self sense. Did you get bigger, smaller, or stay the same?
Same with smell. With the assumption that we are separate, we assume that smells are separate from us. Smells, like all other senses, are happening within. Really focus on smell for a moment (I pray you're not in India right now: peew...). What happens to "you" when you completely give your self to smelling? Did that fixed and solid boundary move? Interesting, isn't it?
Close your eyes (not yet, after you read the sentence) and listen. Notice where the sounds from "outside" enter you and become sounds "inside." Where does that boundary exist? With your eyes closed can you feel that boundary? When you rest your attention at the edge of that boundary, what happens to it?
Listen here and listen good, I am not trying to talk you into a unity experience. That's actually much easier than what I am attempting to do, which is to show you that you are constantly constructing your self-sense and personal boundary (check out this recent post). There is nothing wrong with this construction. At times, it's rather functional. However, it is entirely of your own creation and it is entirely, in its unconscious form, the root of suffering.
Again, freedom is not removing separation for unity. Unity is not enlightenment. Unity is unity. Enlightenment is recognizing that you are the entire universe. Not limited to a unified state, but in each and every form the universe arises in. All of your states are enlightened states. Even the deluded ones.
When the unconscious self-boundary dissolves, there is a lot more space within. The space was always there, mind you. You were just paying attention to the boundary, unconsciously, and the stuff in the space, unconsciously. When the self-constructed boundary of self is seen as a self construction, everything in all space becomes you. You're the space, and you're the stuff in the space, and you're the functional thing you currently call "me."
Within this understanding, all sorts of experiences will unfold: happy experiences, sad experiences, unified experiences, separate experiences (enlightened sex is not simply the universe masturbating), and et al, ad infinitum experience. Everything you experience is enlightened when you recognize all experience as your own self.
This means that you're not separate from other people. No one is doing anything to you. You're not separate from reality either. Reality isn't doing anything to you. Now don't turn this into some new age, The Secret narcissism about creating your own reality. Reality is simply unfolding through you, from you, as you. Awareness experiences the creation of its' own self: everything.
This means that your thoughts, emotions, and actions arise as an expression of awareness. The awareness that is you, but in a much bigger sense than the you as a boundary and the you that is the summation of the inner content of your experience. You are not the originator of these thoughts, feelings, and actions, awareness is.
Adyashanti says: I am nothing, and I am everything.
Nisargadatta said: When I look inside and see that I am nothing, this is wisdom. When I look outside and see that I am everything, this is love. Between these two things, my life unfolds.
Vasugupta said: Consciousness is the Actor. The stage is the inner consciousness. Senses are the spectators. Truth is realized by pure intellect. The state of absolute freedom is already achieved.
Indeed, already acheived.