Nothing. What I'm saying is that we only "exist" in the third person, essentially. That we are merely the perception of a perhaps undefined outer will.
Even from a first person perspective, everything we know is 100% perception. When I look at an object, I percieve that my eyes see it, and when I reach out to it to confirm, I piercieve that my fingers touch it. But is it really there?
I honestly, don't believe so. Not in so many words. I percieve it's there, but in that case, what am I? Where do my perceptions come from? I think of it as sort of a immaterial cloud of consciousness within the "mind" of an trans-universal entity. DesCartes said, "I think, therefore I am." I disagree.
"He thinks, therefore I am."
Remember, all that modern science knows about the physical universe is that it is the product of repulsion and attraction. I cannot occupy the same space as you, because our bodies repulse each other. However, modern science can't explain where that repulsion comes from. You may think, "It comes from atomic charges!" Okay, but what gives an electron a positive charge, and a proton a negative charge. Protons spit out positrons to become neutrons. How does that work? Gluons, of course. We've theorized and postulated into the sub-sub-sub-sub atomic level, and as I said before, we have discovered nothing but space, and more attraction and repulsion. What is the source of the attraction and repulsion? I don't think it will ever be found.
So if the fact that light bounces off of you to make you visible, and the fact that I can't stand inside of you makes you solid, are not at all the result of physical contact on any level, but are simply the result of magnetic forces that can't be explained. There is, in fact, not even any evidence that we exist, besides our senses, which are, demonstratably, entirely subjective. The only reason any of us have to believe any of us exist is because we can see, hear, smell, and touch each other - all 100% matters of perception. Even following that mindset, the light I employ to percieve you with my eyes never touches you, yet is repelled, the particles I use to percieve your smell never contact my scent centers, the waves that act on my eardrum to percieve your sound never touches my ear drum, and the contact I use to percieve your touch never actually contacted me.
So what is the difference between us and empty space?
Nothing. There's absolutely nothing there.